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/services/session-snapshots.ts

@@ -0,0 +1,51 @@
+import type { Sql } from '../db.js';
+
+export interface AgentSnapshot {
+  id: string;
+  session_id: string;
+  chat_id: string;
+  model: string;
+  agent: string | null;
+  mode: string | null;
+  turn_number: number;
+  messages: unknown[];
+  tool_states: unknown[];
+  created_at: string;
+  updated_at: string;
+}
+
+/** Save or update the agent snapshot for a chat (UPSERT). */
+export async function saveAgentSnapshot(sql: Sql, chatId: string, data: {
+  session_id: string;
+  model: string;
+  agent?: string | null;
+  mode?: string | null;
+  turn_number: number;
+  messages: unknown[];
+  tool_states?: unknown[];
+}): Promise<void> {
+  await sql`
+    INSERT INTO agent_snapshots (session_id, chat_id, model, agent, mode, turn_number, messages, tool_states, updated_at)
+    VALUES (${data.session_id}, ${chatId}, ${data.model}, ${data.agent ?? null}, ${data.mode ?? null}, ${data.turn_number}, ${sql.json(data.messages as never)}, ${sql.json((data.tool_states ?? []) as never)}, clock_timestamp())
+    ON CONFLICT (chat_id)
+    DO UPDATE SET
+      model = EXCLUDED.model,
+      agent = EXCLUDED.agent,
+      mode = EXCLUDED.mode,
+      turn_number = EXCLUDED.turn_number,
+      messages = EXCLUDED.messages,
+      tool_states = EXCLUDED.tool_states,
+      updated_at = clock_timestamp()
+  `;
+}
+
+/** Load the agent snapshot for a chat. Returns null if no snapshot exists. */
+export async function loadAgentSnapshot(sql: Sql, chatId: string): Promise<AgentSnapshot | null> {
+  const rows = await sql<AgentSnapshot[]>`SELECT * FROM agent_snapshots WHERE chat_id = ${chatId}`;
+  return rows[0] ?? null;
+}
+
+/** Delete the agent snapshot for a chat (call when session ends). */
+export async function deleteAgentSnapshot(sql: Sql, chatId: string): Promise<void> {
+  await sql`DELETE FROM agent_snapshots WHERE chat_id = ${chatId}`;
+}