Real weather, real aircraft, a heightfield off the main thread, and instruments

Three things that were built and never connected, connected.

**The weather was already there.** `observe()` has always taken a
`WeatherObservation` and `main.ts` has always passed null, so the cloud,
precipitation, visibility and marine-layer paths in atmosphere.ts had never run
outside a test. The server already shipped NWS, met.no and Open-Meteo, all
configured off. What was actually missing was that a single TERA_ORIGIN_LAT/LNG
served one metro and lied to the other — so weather and traffic are per-region
now, derived from the city's own bounds, and the Bay Area gets its fog while
Long Beach gets its own sky. The route takes ?city= or a validated ?lat=&lng=
and refuses to become an open geocoding proxy for the planet.

**The heightfield moved to a Worker.** 2.3 s of blocked main thread at boot, and
another ~950 ms of point-in-polygon on top of it: the park mask is filled in the
worker now, and block placement samples four corners and only runs the exact
test on a cell that straddles an edge — 8 buildings differ out of 185,036.
createScene is async and takes a Stage as a consequence, and there is a
main-thread fallback because "clone it and it works" has no exception clause.

**Spaces is a chunk you fetch when you reach for the door**, not one everybody
downloads. Same for the godmode tools. The entry chunk is 722 kB rather than
772; three.js is most of what is left and splitting it is a different job.

**Godmode is an instrument panel now** rather than one slider: the date and the
season, not just the hour, so the Meeus moon and the sun's seasonal arc become
visible instead of merely correct; a weather override that says on screen when
it is lying; a frame-time and draw-call readout; and a pose editor that emits a
paste-ready Chapter block, which is the thing that makes adding New York cheap.

Two blockers the review caught:

  - Every city switch leaked 8 GPU textures — one of them a 2048x2048 shadow map
    — and ~10.5 shader programs, and deleteTexture had never been called once in
    the app's lifetime. The renderer was being built per scene; it belongs to the
    canvas, for the life of the page.
  - An upstream fetch that threw rather than returning null skipped the cache
    stamp, so the TTL — the only rate limit on outbound calls — collapsed to one
    upstream request per inbound request, and the caller got a 500.

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

NOTICE

@@ -96,3 +96,34 @@ The flight sources shipped in this repository are a simulator (original work)
 and clients for open community ADS-B feeds. No commercial aviation data
 provider's data is included or redistributed, and no client for a provider
 whose terms prohibit such use is present.
+
+No aircraft position is committed to this repository; the community feeds are
+fetched at runtime by a deployment that has been configured to use one. Where
+adsb.lol answers, the API attaches the credit line that feed asks for and the
+browser displays it in the shortcuts card alongside the weather credits below.
+
+
+WEATHER DATA
+------------
+
+No weather observation is committed to this repository either. The default
+build observes nothing at all and models the sky locally, and the shipped
+sources are all opt-in.
+
+Two of them carry an attribution obligation, and it is met at runtime rather
+than here, because which one applies is a property of the deployment and not of
+the source:
+
+  - MET Norway (met.no)    — CC BY 4.0
+  - Open-Meteo.com         — CC BY 4.0
+
+The API emits the credit line each of them asks for in the `attribution` array
+on the weather body, and the browser displays whatever it is sent, for as long
+as that source is what is on screen. See `server/src/weather/` for the strings
+and `renderCredits` in `src/main.ts` for where they land. A deployment that
+turns one of these on and strips the credit is the party in breach, not this
+repository — but the plumbing to comply ships working, on purpose.
+
+The US National Weather Service (api.weather.gov) is a United States government
+work in the public domain and carries no such obligation, which is why it sends
+no attribution array; claiming one would be inventing a licence term.