fix(overpass): keep proxied traffic out of the direct-loopback admission reserve; keep a measured arrival-angle failure through a reveal timeout

- /api/overpass: a loopback socket with forwarding headers (a local reverse
  proxy) is admitted from the remote pool under a socket-keyed proxied: bucket,
  never the owner's direct-loopback window; the upstream limiter uses the same
  key. Regression: owner cache hits survive an exhausted proxy bucket.
- Arrival check: a reveal timeout keeps the settle angle it measured; the new
  observeArrivalRotationWithRetry retries only inconclusive timeouts, so a
  real violation cannot be retried into a pass. Regression: wrong settle angle
  -> reveal timeout -> clean second attempt still fails.
- SECURITY.md, README, changelog and CURRENT-STATE: scope the guarantee to
  admission isolation, name the forwarding headers a local proxy must send,
  and state that the upstream budget stays shared.

docs/CURRENT-STATE.md

@@ -2843,9 +2843,12 @@ down | auth-failed` (plus the unchanged `missing-key`/`unsupported`) with
 > - **Overpass cache admission:** `/api/overpass` refuses cross-site POSTs
 >   through the keyless same-site gate (reverse-proxy forwarding headers are
 >   admitted, as for `/api/terrain/heights`), then limits requests to 300/min
->   per peer — IPv6 peers keyed by /64 — and 900/min across all non-loopback
->   peers before reading or validating bodies; loopback has its own 300/min
->   window outside that global.
+>   per peer — IPv6 peers keyed by /64 — and 900/min across all remote peers
+>   before reading or validating bodies. Direct loopback (no forwarding
+>   headers) has its own 300/min window outside that global; a local reverse
+>   proxy's requests carry forwarding headers and are counted as remote, keyed
+>   `proxied:<socket peer>`, so they cannot spend the owner's window. Upstream
+>   quota stays shared, so owner cache misses can still hit 429.
 >   Tag-filter brackets are scanned once; nested or unmatched brackets return 400.
 >   It then checks fresh memory, identical in-flight work, and fresh disk entries
 >   before invoking its separate local 90/min upstream limiter. Cache and
@@ -5122,7 +5125,7 @@ pins and share links already supply complete boxes.
 - Fleet model eligibility is distance-based with on-screen priority and hard caps (`MODEL_MAX`, `MODEL_MAX_ALL`) to avoid draw-call explosions. Each model owns its own `modelMatrix`; shared scratch matrices are forbidden because they caused stacking/flicker.
 - Tracked aircraft use standalone model primitives driven from the already-settled dead-reckoned display position, while the tracked Cesium entity remains billboard-backed so `viewer.trackedEntity` always has a ready bounding sphere.
 - Flights and military layers mirror the same tracking invariants: no warm-up freeze/jump, altitude-scaled framing, trail head glued to the displayed plane, no pull-out when switching targets, and no cross-layer orphan when switching between commercial and military tracks.
-- Regression surface: `npm run test:track` drives the real app headless with synthetic aircraft feeds and asserts the tracking invariants without depending on live OpenSky/adsb data. Arrival-rotation checks observe the settle frame and then the first reveal frame, each within a 500 ms wall-clock budget that sits inside the one-second idle fallback, rather than assuming the 80 ms fleet cadence fits inside four rendered frames; an incorrect first orientation fails immediately. `src/data/trackedModelRegime.test.mjs` pins the tracked contact's threshold math, the enter/exit asymmetry, and the default-on / cockpit / TR-3B / deselect wiring in both layers.
+- Regression surface: `npm run test:track` drives the real app headless with synthetic aircraft feeds and asserts the tracking invariants without depending on live OpenSky/adsb data. Arrival-rotation checks observe the settle frame and then the first reveal frame, each within a 500 ms wall-clock budget that sits inside the one-second idle fallback, rather than assuming the 80 ms fleet cadence fits inside four rendered frames; an incorrect first orientation fails immediately. Only an inconclusive timeout is retried (once); a timeout that already measured a wrong settle angle keeps it and fails without retry. `src/data/trackedModelRegime.test.mjs` pins the tracked contact's threshold math, the enter/exit asymmetry, and the default-on / cockpit / TR-3B / deselect wiring in both layers.
 
 ### TR-3B conversion Easter egg (August 2026)