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>

src/server/wire.ts

@@ -180,6 +180,75 @@ export interface WireAircraft {
   /** Degrees clockwise from true north. */
   heading: number;
   callsign?: string;
+  /**
+   * Metres per second over the ground, when the feed reported a real one.
+   *
+   * SI, like every other quantity on this wire — the feed's own `gs` is knots
+   * and the conversion happens once, in the adapter, for the same reason
+   * `altitude` is not feet. See the note there.
+   *
+   * **This is the field that makes the sky move.** A client that is handed only
+   * positions can interpolate between the last two of them and nothing more, so
+   * every aircraft replays a leg it has already flown, arrives at the newest
+   * known point and then sits perfectly still until the next snapshot lands
+   * five to fifteen seconds later. Carrying the velocity lets the client
+   * dead-reckon — advance each track along its own track angle at its own
+   * speed, every frame — and an aeroplane that is flying stops being a
+   * screenshot of one.
+   *
+   * Absent, never zeroed, and absent covers three different things that must
+   * all behave the same way downstream: a feed that did not report it, a
+   * ground vehicle or parked aircraft reporting `gs: 0.0`, and a
+   * position-only record with a null `track` — dead-reckoning any of those
+   * along an invented heading would be inventing motion, which is worse than
+   * showing none. `engine/flights.ts` holds a track still when this is missing.
+   */
+  groundSpeed?: number;
+  /**
+   * Metres per second, positive climbing, when the feed reported a rate.
+   *
+   * Barometric where the feed has it and geometric otherwise; the two disagree
+   * by a few percent in real air and by nothing this renders. Absent rather
+   * than zero for the same reason as `groundSpeed`: level flight and no
+   * information are different facts, and only one of them may be drawn.
+   */
+  verticalRate?: number;
+  /**
+   * How old the position fix already was when this snapshot was taken, in
+   * seconds — the feed's `seen_pos`.
+   *
+   * Carried because the client is the thing that has to place the aircraft and
+   * it cannot do that without knowing what instant the coordinates describe.
+   * Between the receiver's last message, this box's cache TTL and the browser's
+   * own hold, a fix reaches a viewer several seconds stale, and a dead-reckoner
+   * handed a stale position as if it were current draws the whole sky lagging
+   * by that much. `observedAt` on the body says when the *snapshot* was taken;
+   * this says how far behind that the row already was.
+   *
+   * Small — a fraction of a second on a healthy feed — and worth carrying
+   * anyway, because it is the difference between a client that can reason about
+   * time and one that assumes.
+   */
+  ageSeconds?: number;
+  /**
+   * The tail number the feed published for this airframe, e.g. `"N68834"`.
+   *
+   * ODbL data off the same record as the position, and publishable on exactly
+   * the same terms — it is the enrichment a commercial feed was once wanted
+   * for, obtained legitimately. Absent, never invented: a registration is what
+   * somebody types into a registry lookup, and a wrong one names another
+   * aircraft altogether.
+   */
+  registration?: string;
+  /**
+   * ICAO aircraft type designator, e.g. `"B739"`, `"A321"`.
+   *
+   * A four-character code and not a marketing name: the feed publishes the
+   * designator, and expanding it to "Boeing 737-900" would mean shipping a
+   * table this repo would then have to keep true. The card shows the code
+   * beside the registration, which is how a spotter reads it anyway.
+   */
+  type?: string;
   /**
    * The transponder's 24-bit ICAO address, lowercase hex, when the feed gave a
    * real one.