feat(tools): mission tool family (engine v2)

Exposes the engine-v2 mission framework to the LLM via seven built-in
tools: mission_create, mission_list, mission_update, mission_delete,
mission_fire, mission_pause, mission_resume.

- src/tools/builtin/mission.rs (new, +705): the seven Tool impls.
  Each holds an Arc<MissionManager>; cadence strings parse into
  MissionCadence (cron / event: / webhook: / manual).
- src/tools/builtin/mod.rs: module + Tool re-exports.
- src/tools/registry.rs:
  - PROTECTED_TOOL_NAMES gains the seven mission_* entries.
  - New pub type MissionSlot — Arc<RwLock<Option<(Arc<MissionManager>,
    ProjectId)>>> — for tools whose registration pre-dates the
    engine's MissionManager construction.
  - mission_slot field on ToolRegistry + public accessor.
  - set_mission_slot(manager, project_id) to populate the slot.
  - register_mission_tools(manager, project_id): instantiates all
    seven tools against the supplied manager and fills the slot.
- src/bridge/router.rs init_engine(): calls
  agent.tools().register_mission_tools(...) once MissionManager is
  constructed, immediately before the bootstrap/resume calls.

Motivating use case: downstream integration tools (e.g. Abound's
send-wire wait-action in nearai/ironclaw-abound) need to create
missions via the generic engine-v2 surface. With this PR, a
downstream fork can register additional mission-using tools through
`ExternalToolRegistrar` (see #2871) and read the MissionManager
through the shared MissionSlot at execute time.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: pranavraja99

src/bridge/router.rs

@@ -1826,6 +1826,15 @@ pub async fn init_engine(agent: &Agent) -> Result<(), Error> {
     mission_manager_inner =
         mission_manager_inner.with_insights_interval(missions_config.insights_interval);
     let mission_manager = Arc::new(mission_manager_inner);
+    // Register the engine-v2 mission tool family now that the manager
+    // exists. Tools constructed here capture `Arc::clone(&mission_manager)`
+    // directly; the call also fills `ToolRegistry::mission_slot` so any
+    // downstream integration tool registered through the plugin seam
+    // (see `ExternalToolRegistrar`) sees the same manager.
+    agent
+        .tools()
+        .register_mission_tools(Arc::clone(&mission_manager), project_id)
+        .await;
     if let Err(e) = thread_manager.recover_project_threads(project_id).await {
         debug!("engine v2: recover_project_threads failed: {e}");
     }