perf(mobile): skip model projection after discovery owner retires (#35540)

* perf(mobile): skip model projection for retired discovery owners

* test(mobile): drop spy-only model discovery projection test

Existing hook suite already covers stale-result exclusion; the new file only asserted a namespace spy call.

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Co-authored-by: OrcaWin <293788423+OrcaWin@users.noreply.github.com>

mobile/src/session/use-mobile-native-chat-model-discovery.ts

@@ -68,8 +68,11 @@ export function useMobileNativeChatModelDiscovery(args: {
     let cancelled = false
     void runRpcOperation(client, discoverModels, { worktree: `id:${worktreeId}`, agentId: agent })
       .then((discovery) => {
+        if (cancelled) {
+          return
+        }
         const models = discovery ? catalogModelsFromModelDiscovery(agent, discovery) : null
-        if (!cancelled && models !== null) {
+        if (models !== null) {
           setResult({ client, scope, models: mergeDiscoveredCatalogModels(agent, catalog, models) })
         }
       })