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/infrastructure/Cargo.toml

@@ -8,12 +8,18 @@ description = "IdeA — infrastructure layer: concrete adapters implementing the
 
 [dependencies]
 domain = { workspace = true }
+# The orchestrator filesystem watcher (driving adapter, ARCHITECTURE §14.3) drives
+# the application's `OrchestratorService`; infrastructure may depend on application.
+application = { workspace = true }
 # `process` (additive) powers LocalProcessSpawner; the workspace baseline keeps
 # rt/macros/sync/fs/io-util.
-tokio = { workspace = true, features = ["process"] }
+tokio = { workspace = true, features = ["process", "time"] }
 uuid = { workspace = true }
 async-trait = { workspace = true }
 serde = { workspace = true }
 serde_json = { workspace = true }
 portable-pty = "0.9"
 git2 = { workspace = true }
+# Filesystem change notifications used to *wake* the orchestrator poll loop early
+# (the poll loop remains the robust cross-platform correctness guarantee).
+notify = "6"