fix(traffic): the traffic layer reads STALE, not LIVE, on cached flow tiles

Once the TomTom tile budget is spent, or TomTom fails, the proxy serves
cached tiles marked STALE-BUDGET / STALE-ERROR. flowSource works out
`stale`, but the layer fetched flow through fetchFlowForBounds, which
returns only the segments, so getStats() and the sync chip still read
"LIVE · Roads: …". #1239 fixed the get_traffic_flow tool the same way; the
layer now uses fetchFlowDetail too, reports stale and oldestTileAt in its
stats, and the chip reads "STALE · Roads: <source> · Flow: cached TomTom
tiles". A source without fetchFlowDetail keeps the previous behaviour.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/CURRENT-STATE.md

@@ -5651,7 +5651,10 @@ easier to meet (detection is now on more often), but does not create it.
   coverage number. `stats.loading` covers outstanding flow work as well as the
   road fetch, so a flow failure landing after the first paint still ends the
   shared loading batch as LOAD FAILED. Harnesses must gate on `!stats.error`,
-  never on `mode === 'live'` alone.
+  never on `mode === 'live'` alone. When the drawn flow came from the proxy's
+  cached STALE-BUDGET / STALE-ERROR tiles, `getStats()` reports `stale: true`
+  and `oldestTileAt`, the row reads STALE, and the sync chip reads
+  `STALE · Roads: <source> · Flow: cached TomTom tiles` instead of LIVE.
 - Traffic runs in `sim` mode (white dots, hardcoded speeds) unless `TOMTOM_API_KEY`
   is configured (env or Keychain `tomtom-api`/`api-key`), which enables `live` mode:
   TomTom flow vector tiles via the budget-governed `/api/tomtom` proxy