fix: stable session IDs for chat/task context persistence

- Chat messages use 'chat-{chat_id}' session → conversation history preserved
- Task messages use 'task-{task_id}' session → task context preserved
- Previously every message created a new random session (no memory)

src/router.ts

@@ -87,6 +87,7 @@ export class EventRouter {
       let collectedText = '';
       for await (const msg of runAgent(prompt, {
         workDir: this.config.workDir,
+        sessionId: `task-${task.id}`,
         model: this.config.model,
         provider: this.config.provider,
         systemPrompt: this.config.prompt || undefined,
@@ -155,9 +156,13 @@ export class EventRouter {
     this.log.info('│  MESSAGE from @%s: "%s"', authorSlug, content.slice(0, 200));
     this.log.info('│  Context: %s | Mentioned: %s', taskId ? `task=${taskId}` : chatId ? `chat=${chatId}` : 'none', isMentioned);
 
+    // Stable session ID per chat/task context — preserves conversation history
+    const sessionId = chatId ? `chat-${chatId}` : taskId ? `task-${taskId}` : `msg-${Date.now()}`;
+
     let collectedText = '';
     for await (const msg of runAgent(content, {
       workDir: this.config.workDir,
+      sessionId,
       model: this.config.model,
       provider: this.config.provider,
       systemPrompt: this.config.prompt || undefined,