fix: Reset AbortController before starting generator to prevent infinite abort loop

When a generator exits with wasAborted=true, the AbortController remains in
aborted state but generatorPromise is set to null. When a new observation
arrives, ensureGeneratorRunning() sees generatorPromise=null and tries to
start a new generator, but the new generator immediately sees
signal.aborted=true and exits, causing an infinite "Generator aborted" loop.

This fix resets the AbortController if it's already aborted before starting
a new generator, allowing the session to recover from the stuck state.

Bug reproduction:
1. Session receives observations
2. Something causes the generator to be aborted
3. generatorPromise = null, but abortController.signal.aborted = true
4. New observation arrives → starts generator → immediately aborted → loop

Fix: Check if abortController.signal.aborted before starting generator,
and create a new AbortController if needed.

src/services/worker/http/routes/SessionRoutes.ts

@@ -122,6 +122,16 @@ export class SessionRoutes extends BaseRouteHandler {
   ): void {
     if (!session) return;
 
+    // Reset AbortController if it was previously aborted
+    // This fixes the bug where a session gets stuck in an infinite "Generator aborted" loop
+    // after its AbortController was aborted (e.g., from a previous generator exit)
+    if (session.abortController.signal.aborted) {
+      logger.debug('SESSION', 'Resetting aborted AbortController before starting generator', {
+        sessionId: session.sessionDbId
+      });
+      session.abortController = new AbortController();
+    }
+
     const agent = provider === 'openrouter' ? this.openRouterAgent : (provider === 'gemini' ? this.geminiAgent : this.sdkAgent);
     const agentName = provider === 'openrouter' ? 'OpenRouter' : (provider === 'gemini' ? 'Gemini' : 'Claude SDK');