feat(live-atc): forward aircraft position, un-throttle bridge polling

- NormalizedTelemetry carries lat/lon (0/0 no-GPS guard, position in the
  change-detection signature) so the backend can derive distance triggers
- bridge polling moves from setInterval to a Worker tick: with the sim in the
  foreground the /live-atc tab is backgrounded and Chrome throttles plain
  intervals to ~1/min — telemetry-driven ATC lagged behind the silence fallback

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/composables/useRadioBackend.ts

@@ -41,8 +41,10 @@ export interface NormalizedTelemetry {
     vs_fpm?: number               // vertical speed, feet/min (+climb, -descent)
     heading_deg?: number          // magnetic heading, 0..360
     on_ground?: boolean           // wheels on the ground
-    distance_to_dest_nm?: number  // great-circle nm to destination airport
-    distance_to_dep_nm?: number   // great-circle nm from departure airport
+    // Raw position in degrees. The backend derives distance_to_dep_nm /
+    // distance_to_dest_nm from these via the session's airport ICAO codes.
+    lat?: number
+    lon?: number
 }
 
 export interface ReadbackFieldDetail {

app/composables/useSimBridgeSync.ts

@@ -1,6 +1,7 @@
 import { computed, onMounted, onUnmounted, ref, watch, type Ref } from 'vue'
 import { useRoute } from 'vue-router'
 import { normalizeSimFreq, normalizeBridgeTelemetry, telemetrySignature } from '../../shared/utils/bridgeTelemetry'
+import { createIntervalWorker } from '../../shared/utils/intervalWorker'
 import { pmLog } from '../../shared/utils/pmLog'
 import type { SimControlCommandResult } from '../../shared/utils/simControl'
 import type { useFrequencyPresets } from '~/composables/useFrequencyPresets'
@@ -60,7 +61,11 @@ export function useSimBridgeSync(
   // Telemetry older than this means the bridge stopped posting.
   const BRIDGE_TELEMETRY_STALE_MS = 12_000
   const BRIDGE_POLL_INTERVAL_MS = 3_000
-  let bridgePoller: ReturnType<typeof setInterval> | null = null
+  // Worker-based ticker: the intended setup is the sim (or WebSim tab) in the
+  // foreground and /live-atc in the background, where a plain setInterval gets
+  // throttled to ~1/min — telemetry-driven ATC (airborne handoff, level checks)
+  // would lag by up to a minute. A Worker tick isn't throttled.
+  let bridgePoller: { stop: () => void } | null = null
   // Last sim active frequency we pushed into the radio — only re-tune active when
   // the sim value actually changes, so manual/flow tuning isn't constantly
   // overridden. Standby has no such anchor: while connected it strictly mirrors
@@ -184,12 +189,12 @@ export function useSimBridgeSync(
     stopBridgeSync()
     if (!bridgeToken.value) return
     void pollBridgeTelemetry()
-    bridgePoller = setInterval(pollBridgeTelemetry, BRIDGE_POLL_INTERVAL_MS)
+    bridgePoller = createIntervalWorker(BRIDGE_POLL_INTERVAL_MS, () => void pollBridgeTelemetry())
   }
 
   function stopBridgeSync() {
     if (bridgePoller) {
-      clearInterval(bridgePoller)
+      bridgePoller.stop()
       bridgePoller = null
     }
   }