feat(orchestrator): file-based orchestrator request watcher (§14.3)

- domain: OrchestratorRequest/Command parse-don't-validate + OrchestratorRequestProcessed event
- application: OrchestratorService dispatching spawn/stop/update_agent_context
- infrastructure: request watcher over .ideai/requests/, writes .response.json
- app-tauri: relay OrchestratorRequestProcessed to the frontend DTO

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/app-tauri/src/events.rs

@@ -91,6 +91,16 @@ pub enum DomainEventDto {
         /// Project id.
         project_id: String,
     },
+    /// An orchestrator request was processed on behalf of a requester agent.
+    #[serde(rename_all = "camelCase")]
+    OrchestratorRequestProcessed {
+        /// Id of the requesting (orchestrator) agent.
+        requester_id: String,
+        /// The action that was processed.
+        action: String,
+        /// Whether IdeA handled it successfully.
+        ok: bool,
+    },
     /// Raw PTY output (normally routed to a per-session channel, not here).
     #[serde(rename_all = "camelCase")]
     PtyOutput {
@@ -147,6 +157,15 @@ impl From<&DomainEvent> for DomainEventDto {
             DomainEvent::GitStateChanged { project_id } => Self::GitStateChanged {
                 project_id: project_id.to_string(),
             },
+            DomainEvent::OrchestratorRequestProcessed {
+                requester_id,
+                action,
+                ok,
+            } => Self::OrchestratorRequestProcessed {
+                requester_id: requester_id.clone(),
+                action: action.clone(),
+                ok: *ok,
+            },
             DomainEvent::PtyOutput { session_id, bytes } => Self::PtyOutput {
                 session_id: session_id.to_string(),
                 bytes: bytes.clone(),