feat: agent session management — metrics, channels, dispose (P2-006) (#78)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/gateway/src/agent/agent.service.ts

@@ -12,6 +12,7 @@ import { CoordService } from '../coord/coord.service.js';
 import { ProviderService } from './provider.service.js';
 import { createBrainTools } from './tools/brain-tools.js';
 import { createCoordTools } from './tools/coord-tools.js';
+import type { SessionInfoDto } from './session.dto.js';
 
 export interface AgentSessionOptions {
   provider?: string;
@@ -25,6 +26,9 @@ export interface AgentSession {
   piSession: PiAgentSession;
   listeners: Set<(event: AgentSessionEvent) => void>;
   unsubscribe: () => void;
+  createdAt: number;
+  promptCount: number;
+  channels: Set<string>;
 }
 
 @Injectable()
@@ -107,6 +111,9 @@ export class AgentService implements OnModuleDestroy {
       piSession,
       listeners,
       unsubscribe,
+      createdAt: Date.now(),
+      promptCount: 0,
+      channels: new Set(),
     };
 
     this.sessions.set(sessionId, session);
@@ -143,11 +150,53 @@ export class AgentService implements OnModuleDestroy {
     return this.sessions.get(sessionId);
   }
 
+  listSessions(): SessionInfoDto[] {
+    const now = Date.now();
+    return Array.from(this.sessions.values()).map((s) => ({
+      id: s.id,
+      provider: s.provider,
+      modelId: s.modelId,
+      createdAt: new Date(s.createdAt).toISOString(),
+      promptCount: s.promptCount,
+      channels: Array.from(s.channels),
+      durationMs: now - s.createdAt,
+    }));
+  }
+
+  getSessionInfo(sessionId: string): SessionInfoDto | undefined {
+    const s = this.sessions.get(sessionId);
+    if (!s) return undefined;
+    return {
+      id: s.id,
+      provider: s.provider,
+      modelId: s.modelId,
+      createdAt: new Date(s.createdAt).toISOString(),
+      promptCount: s.promptCount,
+      channels: Array.from(s.channels),
+      durationMs: Date.now() - s.createdAt,
+    };
+  }
+
+  addChannel(sessionId: string, channel: string): void {
+    const session = this.sessions.get(sessionId);
+    if (session) {
+      session.channels.add(channel);
+    }
+  }
+
+  removeChannel(sessionId: string, channel: string): void {
+    const session = this.sessions.get(sessionId);
+    if (session) {
+      session.channels.delete(channel);
+    }
+  }
+
   async prompt(sessionId: string, message: string): Promise<void> {
     const session = this.sessions.get(sessionId);
     if (!session) {
       throw new Error(`No agent session found: ${sessionId}`);
     }
+    session.promptCount += 1;
     try {
       await session.piSession.prompt(message);
     } catch (err) {
@@ -177,7 +226,13 @@ export class AgentService implements OnModuleDestroy {
     } catch (err) {
       this.logger.error(`Failed to unsubscribe session ${sessionId}`, String(err));
     }
+    try {
+      session.piSession.dispose();
+    } catch (err) {
+      this.logger.error(`Failed to dispose piSession for ${sessionId}`, String(err));
+    }
     session.listeners.clear();
+    session.channels.clear();
     this.sessions.delete(sessionId);
   }