feat: Paseo-like orchestrator Phase 1-2 — trace system, session persistence, timeline, run_command, auto-fix loop

Phase 1: Trace System + Observability
- tool_traces DB table + insert/update service
- tool_trace_start/tool_trace_finish WS frames (contracts + FE types)
- Instrumented tool-phase.ts with timing around every tool call
- GET /api/chats/:id/traces paginated endpoint
- Trace viewer frontend (collapsible panel with timing bars + token breakdown)

Phase 2: Session Persistence + Resume
- agent_snapshots table (UPSERT per chat, persisted on turn boundaries)
- save/load/delete service functions
- Agent snapshot sent on WS reconnect
- Session timeline view (vertical timeline with scroll-to + restore)

Tooling:
- run_command tool (execFile, 30s timeout, 32KB cap, path-guarded)
- Auto-fix loop: after write tools, runs pnpm build, injects errors into next turn

apps/server/src/routes/traces.ts

@@ -0,0 +1,38 @@
+import type { FastifyInstance } from 'fastify';
+import type { Sql } from '../db.js';
+import type { ToolTrace } from '../services/tool-traces.js';
+
+export function registerTraceRoutes(app: FastifyInstance, sql: Sql): void {
+  app.get<{ Params: { id: string }; Querystring: { limit?: string; offset?: string } }>(
+    '/api/chats/:id/traces',
+    async (req, reply) => {
+      const chat = await sql`SELECT id FROM chats WHERE id = ${req.params.id}`;
+      if (chat.length === 0) {
+        reply.code(404);
+        return { error: 'chat not found' };
+      }
+
+      const limit = Math.min(Math.max(Number(req.query.limit) || 50, 1), 200);
+      const offset = Math.max(Number(req.query.offset) || 0, 0);
+
+      const rows = await sql<ToolTrace[]>`
+        SELECT * FROM tool_traces
+        WHERE chat_id = ${req.params.id}
+        ORDER BY started_at ASC
+        LIMIT ${limit}
+        OFFSET ${offset}
+      `;
+
+      const [countRow] = await sql<{ count: number }[]>`
+        SELECT count(*)::int AS count FROM tool_traces WHERE chat_id = ${req.params.id}
+      `;
+
+      return {
+        data: rows,
+        total: countRow?.count ?? 0,
+        limit,
+        offset,
+      };
+    },
+  );
+}