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/domain/src/lib.rs

@@ -37,6 +37,7 @@ pub mod git;
 pub mod ids;
 pub mod layout;
 pub mod markdown;
+pub mod orchestrator;
 pub mod ports;
 pub mod profile;
 pub mod project;
@@ -79,6 +80,8 @@ pub use layout::{
 
 pub use events::DomainEvent;
 
+pub use orchestrator::{OrchestratorCommand, OrchestratorError, OrchestratorRequest};
+
 pub use ports::{
     AgentContextStore, AgentRuntime, Clock, ContextInjectionPlan, DirEntry, EventBus, EventStream,
     ExitStatus, FileSystem, FsError, GitCommitInfo, GitError, GitFileStatus, GitPort, GraphCommit,