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]>

src/layers/traffic/model.js

@@ -229,6 +229,7 @@ export function createModel({ state: layerState, services, parts, source }) {
    * @param {boolean} [input.liveMode] - `/api/tomtom/status` reported a key.
    * @param {boolean} [input.fetching] - A viewport load is in flight.
    * @param {string|null} [input.flowError] - `deriveTrafficFlowError` result, if any.
+   * @param {boolean} [input.stale] - The flow came from cached proxy tiles.
    * @param {number} [input.coveragePct] - Share of shown dots on matched roads, 0–100.
    * @param {boolean} [input.statusUnavailable] - The status probe itself failed.
    * @param {string} [input.roadSource] - Name of the geometry being drawn.
@@ -239,6 +240,7 @@ export function createModel({ state: layerState, services, parts, source }) {
     liveMode = false,
     fetching = false,
     flowError = null,
+    stale = false,
     coveragePct = 0,
     statusUnavailable = false,
     roadSource = 'OpenStreetMap',
@@ -258,6 +260,16 @@ export function createModel({ state: layerState, services, parts, source }) {
       });
       return { mode, error: degraded, loadingLabel: degraded };
     }
+    // Cached proxy tiles (TomTom budget spent or upstream failing) are not live.
+    if (liveMode && stale && !fetching) {
+      return {
+        mode,
+        error: null,
+        loadingLabel: t('STALE · Roads: {source} · Flow: cached TomTom tiles', {
+          source: roadSource,
+        }),
+      };
+    }
     // TomTom and Hybrid name their geometry; OpenStreetMap keeps its match copy.
     if (liveMode && roadSource === 'TomTom') {
       return {