fix(runtime): stop gating pi tool calls; Co-Founder approvals live at API layer

The Co-Founder beforeToolCall hook (introduced in 77f81a7) gated every
non-readonly pi tool call as a `dangerous_command` approval. Because
agents call `POST /api/companies/:id/messages`, `/agents` (hire), and
every other company mutation via bash→node/curl, the first bash call in
every Co-Founder run got parked on a 30-minute approval timeout. Users
observed it as "agents never talk to each other" and "every bash command
waits for approval"; both symptoms are the same bug.

The business-level approval flow (`hire_agent`, `document_review`,
`plan_review`, etc. in execution-policy.ts) already gates the events
users actually care about, at the HTTP route layer where the event
originates (routes-agents.ts:368 for hiring, document routes for
deliverables). Stacking a pi-level hook on top was duplicate gating with
the wrong taxonomy.

Removed:
- src/main/agent-runtime/approval-hook.ts (entire file, 137 LOC)
- `beforeToolCall` conditional in worker-runner.ts and the
  corresponding RPC method in worker-types.ts and runtime-bridge.ts
- `approvalHook` field + `resolveApproval` callback + shutdown
  `cancelAll` in runtime-bridge.ts / service-graph-pi-runtime.ts /
  wire-api-server.ts

Unchanged:
- `dangerous_command` approval type itself (still used by automation
  workflows and routes-misc.ts)
- CEO mode (already never attached the hook)
- All business-level approval types and their wiring

src/main/service-graph-pi-runtime.ts

@@ -51,8 +51,6 @@ export function createPiRuntimeServices(deps: PiRuntimeServicesDeps): PiRuntimeS
     credentialResolver,
     oauthLoginService,
     runtimeBridge,
-    release: () => {
-      runtimeBridge.approvalHook.cancelAll("AgentCompany shutting down.");
-    },
+    release: () => {},
   };
 }