feat(directions): keyless A→B directions with turn-by-turn steps and FLY (#564)

Supersedes #219 by @spcpza, ported onto the current component layout with fixes from review.

Verified before merge: format, package boundaries, unit suite, build, and the browser tracking suite; a browser harness for the change where one applies; adversarial review applied.

Co-authored-by: spcpza <[email protected]>

DATA_SOURCES.md

@@ -48,6 +48,7 @@ How to read this:
 | **GBFS (Lyft / BCycle)**                                              | Bikeshare availability                                                                                                              | Per-feed (attribution-only)                                                                                                                                                                                                                                                                                                                           | Credit the operator (e.g. Austin BCycle) + its `license_url`                                                                                |
 | **Radio Browser**                                                     | Geolocated internet-radio station directory and station-level tags                                                                  | Public-domain directory data under PDDL 1.0; individual broadcaster stream terms apply                                                                                                                                                                                                                                                                | "Radio Browser" plus a link to the selected broadcaster                                                                                     |
 | **Re:Earth Terrain** (Mapterhorn)                                     | Terrain (keyless globe stacks — OSM etc. — + `/api/terrain/heights` ellipsoidal-height lookups)                                     | Terrain mesh: CC BY 4.0; geoid: EGM2008 (NGA, public domain)                                                                                                                                                                                                                                                                                          | "Terrain (keyless globe stacks): Re:Earth Terrain / Mapterhorn (CC BY 4.0) / EGM2008 (NGA)"                                                 |
+| **OSRM on the FOSSGIS routing servers** (`routing.openstreetmap.de`) | Street-following routes for the Directions layer and voice route annotations, via `/api/route` | [FOSSGIS routing usage policy](https://routing.openstreetmap.de/about.html): "Display the required attribution and display a link to 'fix the map'", "Use a valid user agent and, if applicable, a correct referrer", "One request per second max", "No scraping, no heavy usage". The full policy is the German [FOSSGIS Nutzungsbedingungen](https://www.fossgis.de/arbeitsgruppen/osm-server/nutzungsbedingungen/); FOSSGIS also states that the server may be embedded in your own pages but "eine gewerbliche Nutzung ist nur mit Einschränkungen erlaubt" (commercial use only with restrictions). Route data derives from OpenStreetMap (ODbL 1.0) | "Routing: OSRM on the FOSSGIS servers" + "© OpenStreetMap contributors" + a "fix the map" link — shown in the Data attribution popover |
 
 ### Notes on the live sources
 
@@ -68,7 +69,9 @@ How to read this:
 - **Camera frame content.** Public camera frames can contain people, vehicles and license plates, and the camera layer does nothing with them beyond putting them on the map. A successful upstream response is relayed as the provider served it: nothing in the camera pipeline blurs, redacts, enhances or restores it, and nothing there runs face, plate or object detection or otherwise recognises or classifies what is in the picture. (The ALPR layer described below maps where plate-reader cameras are, from locations contributors tagged in OpenStreetMap; it reads nothing from any camera frame.) When an upstream has no frame for a camera, what you see instead is a Google Street View still or the app's own placeholder card; the panel's source badge names which of them you are looking at, and a refresh that fails after a frame has arrived leaves the last good picture on screen rather than replacing it. The browser resamples each frame for display: onto a fixed 1920x1080 surface for the camera's projection plane in the scene, and onto a 192x108 canvas for the small ambient card. That scaling is the only change made to the picture, and the only pixels the camera layer reads back are a 64x36 downscale hashed to tell whether the picture has changed. Live streams are piped through; the still path reads the image into memory to pass it on — TxDOT wraps its JPEG in a JSON envelope, which is decoded there — and no frame is written to disk (the disk cache, `.gev-cache/`, holds feed JSON for other layers and never camera imagery). Outside that pipeline, the voice assistant is the one feature that sends imagery anywhere: when it answers a question about what is in view it may attach a downscaled screenshot of the rendered scene — including any camera plane on screen — to the request it sends to the voice model. Frames are fetched only from server-registered camera URLs — a client cannot hand the proxy a URL (see [SECURITY.md](SECURITY.md)). What the app does stays inside the line README draws: no named-person search, no face recognition, no tracking individuals.
 - **Radio Browser.** `/api/radio/stations` discovers official API mirrors, makes bounded and coalesced healthy/geolocated HTTPS-station queries, caches the normalized public-domain directory for 45 minutes, and may serve the last good catalog for up to seven days during an outage. Refreshes must meet minimum accepted-query and station coverage before replacing a warm catalog; schema-valid responses whose rows all fail the product's health policy do not count as successful queries. A usable partial cold catalog is explicitly `DEGRADED`, and malformed or empty successful payloads are rejected atomically. Every directory and click-count request rejects redirects, validates all resolved addresses as globally routable (including reserved/documentation IPv4 and special/non-global IPv6 exclusions), and pins the TLS connection to a validated address. Only MP3/AAC non-HLS directory rows with public HTTPS stream targets are returned; favicons are intentionally omitted. Pressing play connects one browser audio element directly to the selected broadcaster and calls the directory's click counter through known-ID-only `POST /api/radio/click/:uuid`. GEV never proxies, caches, records, bundles, or redistributes audio. Radio Browser supplies station-level tags, not dependable current-song or upcoming-program metadata, so Radio filtering never claims either. Direct playback exposes the listener's IP address to the broadcaster, whose own stream terms apply.
 - **TomTom Traffic.** Optional and BYOK: without `TOMTOM_API_KEY` the traffic layer runs its built-in simulation and no TomTom data (or attribution) appears. With a key, flow vector tiles are fetched through the server-side `/api/tomtom` proxy (120 s cache + a daily tile-budget governor — `TOMTOM_DAILY_TILE_BUDGET`, default 40,000, a configurable application safety ceiling, not a guarantee of staying within TomTom's monthly free allowance; TomTom's [current pricing](https://docs.tomtom.com/pricing/) lists 200K free tile requests per month) and the "Traffic flow data © TomTom" credit is registered in the Data attribution popover the moment live mode activates. TomTom data is served live and cached only transiently (≤120 s TTL under `.gev-cache/`, gitignored) — it is not bundled or redistributed. One 23 KB point-in-time tile snapshot is committed as a decode-test fixture (`src/data/fixtures/`, © TomTom, never served to the app).
+- **Routing (OSRM / FOSSGIS).** `/api/route` proxies the public OSRM instances FOSSGIS e.V. runs for the OpenStreetMap community (car, bike, foot profiles). They are keyless and intended for fair, interactive use — the proxy rate-limits clients (60/min, 200/min total), caps route span and response size, caches each route for 10 minutes, and identifies itself in the User-Agent. Heavy or automated use must run its own OSRM. Routes are computed from OpenStreetMap data (ODbL); the Directions layer and voice routes never redistribute them. A route the router cannot find is reported as such; the Directions layer draws nothing in that case, and voice routes fall back to a clearly labeled straight line.
 - **Re:Earth Terrain.** Keyless (no API key). Used two ways: (1) `src/mapStackController.js` swaps in a `Cesium.CesiumTerrainProvider` pointed at Re:Earth's `cesium-mesh/ellipsoid` quantized-mesh endpoint for globe stacks without a Cesium ion token (e.g. OSM), replacing a flat `EllipsoidTerrainProvider`; falls back to the flat provider if the endpoint can't be reached. (2) The server-side `/api/terrain/heights` proxy (disk-cached, serve-stale) resolves per-point ellipsoidal ground height for entity placement. Both are best-effort with a keyless-safe fallback (bundled EGM96 geoid math) if Re:Earth is unreachable.
+- **OSRM on the FOSSGIS routing servers.** Keyless (no API key). Every route is requested by a person: clicking A and B in the Directions layer, or a voice "route from A to B". The server-side `/api/route` proxy sends an identifying `User-Agent`, pins the upstream host, accepts 2-12 coordinates, rejects any leg over 600 km or a total over 2,500 km, caps the buffered response at 8 MB, times the upstream out at 12 s, rate-limits per client, caches each route for 10 minutes, and coalesces identical requests that are in flight at the same time. Turn-by-turn maneuvers are asked for only when a caller wants them (`steps=1`), so the callers that do not read them send the smaller request. The "fix the map" link the policy asks for is in the Data attribution popover beside the OpenStreetMap credit.
 - **Global Context installation context.** `/api/military-installations` queries only an allow-listed subset of OSM `military=*` and `landuse=military` features inside a maximum 10° non-dateline viewport. It caches and may serve stale mapped context, but it is neither a global installation database nor evidence of capability, activity, or absence. User-requested Google Places results remain separately sourced candidates unless their returned types explicitly establish military classification; generic offices, museums, and similarly ambiguous matches are excluded from military proximity counts.
 - **Cockpit regional briefing.** `/api/regional-brief` rounds aircraft coordinates into 0.1° cache cells, caches results for five minutes, and serializes Nominatim calls at no more than one request per second. Google News RSS is queried with the resolved locality/region first; GDELT is used only when that RSS query fails or is empty. Google's published Google News terms restrict that source to personal, noncommercial use, so commercial deployments must disable/replace it or obtain separate permission; GDELT permits commercial dataset use with citation. The Data attribution popover identifies the active headline sources; article links retain publisher attribution. Headlines are location-query matches, not verified incidents, risk rankings, or evidence that a location is safe. Empty, partial, stale, and unavailable source states remain distinct. Open-Meteo supplies current conditions independently of the news source. `WX OFF` disables cockpit weather rendering only; the Local Info briefing still fetches its source-backed weather values and displays the required linked Open-Meteo credit.
 - **Dynamic weather presentation.** While cockpit mode is active, `/api/weather-effects` requests current Open-Meteo observations for the aircraft/camera location, rounds coordinates into 0.1° cache cells, caches results for five minutes, and may retain a stale observation for up to 30 minutes during a transient outage. WMO condition code selects the visual family; observed cloud cover, precipitation, visibility, wind speed, and wind direction bound its strength and motion. Missing or expired weather renders no synthetic atmospheric effect, and normal globe view never renders the weather overlay.