fix(transit): keep the real silhouettes under sensor presets, make the selected trail visible, put Transit in Movement (#596)

## Changes

Follow-up to #587 after the owner's first look at the merged transit layer on Google 3D tiles.

- **Sensor presets keep the real silhouettes.** Under NVG, thermal (white-hot, black-hot, Ironbow) and noir, vehicles are the same silhouettes as in normal view, filled opaque white with a 2 px dark halo, at the CRT display sizes (26 px fleet, 39 px selected). The solid rounded "signature" bodies are gone.
- **The selected vehicle's trail is visible.** The retained history is now draped onto 3D tiles and terrain (`GroundPolylinePrimitive`, `ClassificationType.BOTH`, the way the traffic heat-lines are drawn), 3 px core over a 5 px dark backing, per-segment age colour, a short draped head clipped to the sprite. Two defects kept it off screen before: Cesium's per-instance attribute getters return copies, so the renderer's show/colour edits were discarded, and a marker did not recover after the camera jumped to it, which hid the trail with it. Trail geometry is now prepared on selection independent of floor resolution and marker visibility; sparse long intervals (rail) keep a bounded marker corridor instead of dropping the interval; classification survives map-source changes.
- **Transit sits in the Movement panel group** between Street Traffic and Bike Share (the panel orders by `PANEL_GROUPS`, not by catalog order; the catalog is moved too).

## How it was verified

- `npm run format:check` (854 files), `npm run check:boundaries`, `npm test` (4,062 passing), `npm run build` clean; tracking regression 109/109 in a real browser on Google 3D tiles.
- Browser harness (`scripts/qa-transit.mjs`), keyed on Google 3D tiles and keyless: keyed 194 pass, with the trail pixel check passing at 300, 600 and 900 m; the remaining keyed failures are the per-frame allocation gate already recorded as a follow-up from #587 (CPU and frame time within budget), four readability lines at threshold edges, and the card-anchor check now counting frames where the selected marker is legitimately off screen; keyless 193 pass with the remaining misses being threshold edges on the thin tram silhouette (centre 0.83–0.88 against 0.85) and one bus ring 0.28 against 0.25 on a pure-white roof.
- New harness checks: `Google 3D selected trail visible at 6 of 8 projected samples` (repeated off/on framebuffer captures at 300/600/900 m, samples outside the sprite footprint, a background-change negative control; fails on main, passes here), a camera-arrival check (select a moving vehicle, `setView` onto it, marker shown and trail body drawn within 2 s), `PANEL_ORDER` pinned, raster tests comparing every sensor raster's mask and aspect ratio to the normal silhouette.
- Direct look on a keyed build: a live CapMetro bus at 30 m/s selected through the layer API draws its draped trail along the highway lane (harness capture `keyed-600m-trail-visible.jpg`).
- Adversarial review by Codex Astra before the last two fix passes (stack-switch classification, marker corridor under the vertex cap, pixel-gate loophole), all three fixed with regressions.

Docs: `docs/CURRENT-STATE.md` and `CHANGELOG.md` updated in this PR. No data-source changes.

src/layers/transit/rendering.js

@@ -97,6 +97,7 @@ export function createRendering({ state, services, parts }) {
       nearGround,
     );
     entry.surfaceReady = !!known;
+    entry.heightPending = !known;
     entry.marker.show = !!known && vehicleInView(entry);
     if (known) {
       entry.marker.position = state._scratchCartesian;
@@ -523,6 +524,10 @@ export function createRendering({ state, services, parts }) {
       else state._visible.delete(entry);
       if (visible && entry.track?.count) {
         if (!wasVisible && !entry.qaFixture) syncPlayback(entry, now);
+        // Re-entry can advance into an unprepared corridor; loaded tiles can
+        // also resolve a cold path without a poll or a render-loop wakeup.
+        if (!wasVisible || entry.surfaceReady === false || entry.heightPending)
+          parts.trails.prepareEntry(entry);
         // Surface completion must recover while requestRenderMode is idle.
         // Otherwise surfaceReady=false prevents the very frame that clears it.
         if (!state._moving.has(entry)) {
@@ -532,6 +537,8 @@ export function createRendering({ state, services, parts }) {
       }
       entry.marker.show =
         visible && !entry.heightPending && entry.surfaceReady !== false;
+      visibility.heightPending = !!entry.heightPending;
+      visibility.surfaceReady = entry.surfaceReady ?? null;
       schedulePlayback(entry);
       changed ||= visible !== wasVisible || wasShown !== entry.marker.show;
     }