feat: SFO, LAX, both bridges, a road that reads as a road, and aeroplanes that move

**The aeroplanes were stuck because the wire could not describe motion.**
`WireAircraft` carried position, altitude and heading and nothing else, so the
client could only interpolate between the last two observations: every aircraft
replayed a segment it had already flown, arrived at the newest known point, and
sat still until the next poll landed five to fifteen seconds later. The feed had
the missing numbers the whole time and the server threw them away. Sampled live
from `api.adsb.lol/v2/point` while writing this — `gs` ground speed, `track`,
`baro_rate`, plus `r` registration and `t` type designator. They are on the wire
now in SI, aircraft dead-reckon along their own track and correct toward the
truth when a fix lands, and the click card an anonymous visitor gets says
"B739 · N68834". That last part is the enrichment FR24 was wanted for, obtained
from an ODbL feed we may actually republish.

**SFO and LAX exist.** A new `engine/airports.ts` composes an airport from
runways, taxiways, aprons and terminal masses, with markings drawn on a canvas
rather than modelled; the pattern of the runways is what the eye recognises from
altitude, long before any building does. SFO is the two crossing pairs on the bay
fill; LAX is the four parallels either side of the terminal horseshoe, plus the
Southland fields under the traffic that actually flies there.

**The Golden Gate and the Bay Bridge are those bridges.** One kit in
`engine/bridges.ts`, because a suspension bridge is a repeated tower, a catenary
main cable, a series of hangers and a deck — so both are configurations rather
than two private implementations. The Bay Bridge carries the real 2013 topology:
two suspension towers west of Yerba Buena, one east, then the piered causeway.
The freeway stopped being a wireframe overlay and became a road, with shoulders,
a median, and lane markings as texture.

**And the board got faster while all of that landed.** California went from
728,744 triangles and 562 draw calls to 391,169 and 371 — headroom from 2.8% to
47.8%. The Bay Area board is 506,550 triangles lighter than before this work.
Two things paid for it:

- `transmission: 0.08` on the aircraft cockpit glass. three.js runs a full
  transmission backdrop pass whenever any rendered material has transmission
  above zero, re-drawing the entire opaque scene into a second target every
  frame — so the city was rendering terrain, every block and every freeway piece
  TWICE. Measured by patching only that number in a copy of the built bundle:
  703,267 tris / 562 draws with it, 398,608 / 371 without. The material was
  already `transparent: true, opacity: 0.86`, so it was buying nothing.
- Flatness-adaptive terrain LOD, which collapses runs of lattice cells wherever
  the height and colour agree with the quad replacing them. The coastline is
  provably untouched — a patch collapses only when every point is on land and
  agrees about `park` — and a test asserts the drawn footprint matches the
  cell-by-cell area to 1e-6. `createTerrain` got *faster*: the vertices it stops
  emitting cost more than the flatness scan costs to run.

**The budget now watches the boards this was built on.** There was no `bay-area`
or `socal` cell — so SFO, LAX and both bridges all landed in frames nothing
measured, which is how a cap you do not have looks from the inside. Both are in
the matrix now with caps set from measurement, and the rationale lives in the
harness because JSON cannot hold a comment.

Two known defects ship with this, both recorded in TODO.md rather than hidden:

- `bay-area.desktop` drops about one frame in twenty (p50 16.7, p95 33.3). It is
  desktop-only and not fill rate — mobile runs the same 2.26 M triangles at a
  comparable pixel count and holds 16.7 flat — which points at the 2048 shadow
  map desktop uses against handheld's 1024. Measured at the commit before this
  work with the same harness: identical p95 33.3. Pre-existing, and invisible
  until the cell existed.
- The aeroplane glyph is still about 1.5x the Golden Gate's main span at chapter
  zoom, down from 2.5x. `GLYPH_MAX_SCALE` is 52 because the raw scale at the far
  end of the California orbit is 51.0 at a 60-degree field of view, and 26 —
  tried first — put the glyph at 0.0123 of the frame against the 0.012 where the
  wings stop resolving. The real fix is to clamp against the camera's focus
  distance rather than the aircraft's, which is a signature change.

Tests 1020 -> 1137. Typecheck, build, eight budget cells, no-binaries,
provenance, zero-config boot, dependency licences, arena source hashes and the
UI smoke across two viewports and two access tiers all pass.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

TODO.md

@@ -41,3 +41,53 @@ Worth knowing before starting (the rest is in `~/.claude/skills/tera-capture`):
   added there too, because a frame with a stray card in it still renders and still
   looks deliberate.
 - Commit tera first, then re-run, so the manifest records a clean sha.
+
+## The Bay Area board drops a frame in twenty, on desktop only
+
+`bay-area.desktop.p95FrameIntervalMs` carries a **33.4 ms allowance and that is a
+recorded defect, not a target.** The board renders a median frame in 16.7 ms and
+drops roughly one frame in twenty: p50 16.7, p95 33.3, and 443–456 frame samples
+in a window where every other cell returns 480.
+
+It is desktop-only, and it is **not fill rate**: the mobile cell runs the *same*
+2.26 M triangles at a comparable pixel count — 1.32 MP against desktop's 1.30 —
+and holds 16.7 ms flat. The obvious suspect is the shadow map, which `stage.ts`
+sizes **2048 on desktop and 1024 on handheld**, over what is now the heaviest
+shadow-casting scene in the product.
+
+**It is not a regression, and this was checked rather than assumed.** Measured at
+the commit before the airports and bridges landed, with the same harness:
+p95 33.3, p50 16.7, 443 samples, **2,771,606 triangles**. After that work:
+p95 33.3, p50 16.7, 456 samples, **2,265,056 triangles** — the board got
+506,550 triangles *lighter* while gaining SFO, both bridges and a surfaced
+freeway. The stutter was simply invisible until `bay-area` became a measured
+cell, which it had never been.
+
+The allowance is there so the cell still guards the numbers that are healthy —
+triangles, draw calls, and the mobile frame time — rather than sitting
+permanently red and therefore permanently ignored. **Fix the stutter and put the
+cap back to 16.7.** Start with the desktop shadow-map size and the shadow
+frustum over the SF board; a 2048 map over 2.26 M triangles of casters is the
+first thing to rule in or out.
+
+## The aeroplane glyph is still larger than the Golden Gate
+
+`GLYPH_MAX_SCALE` in `src/engine/flights.ts` is 52 and that is a mitigation, not
+a cure. The glyph has a screen-space *floor* — never smaller than legible — which
+scales by the distance to the **aircraft**, when what makes it look wrong is how
+far the camera is from **what it is looking at**. At a whole-board pose those are
+the same thing; at the Golden Gate chapter the bridge is two units from the camera
+and the traffic is two thousand, so the floor fires hard on the aeroplane and not
+at all on the bridge.
+
+A ceiling of 52 was chosen because the raw scale at 1,160 units — the far end of
+the orbit over the California corridor — is 51.0 at a 60-degree field of view, so
+anything lower shrinks aeroplanes at a pose people actually use. (26 was tried
+first and put the glyph at 0.0123 of the frame, against the 0.012 at which
+`flights.ts` says the wings stop resolving.) 52 takes the worst case from about
+two and a half times the bridge's main span down to about one and a half.
+
+The complete fix is to clamp against the camera's focus distance rather than the
+aircraft's, so the glyph collapses toward its authored size whenever the viewer
+has zoomed in on something near, at any aircraft range. That is a signature change
+through `glyphScale`, `tick` and their callers.