feat(session-limits): LS7 — câblage backend app-tauri (taps niveaux 1&2 + reprise annulable)

Branche le SessionLimitService dans l'application Tauri et expose la
surface de reprise/annulation au front.

- application/agent/lifecycle.rs : LaunchAgentOutput.profile exposé
  (None sur réattache/idempotent, Some sur lancement effectif).
- application/terminal/registry.rs : StructuredSessions::meta_for_session()
  (lookup agent/node par SessionId pour le tap niveau 1).
- app-tauri/state.rs : ResumeContext(s), AppAgentResumer (impl du port
  AgentResumer au-dessus de LaunchAgent), instanciation + câblage du
  SessionLimitService (TokioScheduler + drain des réveils) dans AppState::build.
- app-tauri/commands.rs : taps niveau 1 (agent_send) et niveau 2
  (launch_agent, parser regex confiné), alimentation de resume_contexts,
  commande cancel_resume.
- app-tauri/lib.rs : enregistrement de cancel_resume dans le handler.
- app-tauri/Cargo.toml : dépendance async-trait.

Tests : session_limit_wiring.rs (2 tests de composition) + meta_for_session
dans structured_registry_d1.rs ; fixtures dto_agents/dto_chat ajustées
(profile: None). Tout vert.

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

crates/app-tauri/tests/dto_chat.rs

@@ -157,6 +157,7 @@ fn launch_output_with_structured_descriptor_derives_chat_cell_kind() {
         assigned_conversation_id: None,
         engine_session_id: None,
         structured: Some(descriptor),
+        profile: None,
     };
     let dto = TerminalSessionDto::from(out);
     assert_eq!(dto.cell_kind, CellKind::Chat);
@@ -173,6 +174,7 @@ fn launch_output_without_structured_descriptor_derives_pty_cell_kind() {
         assigned_conversation_id: None,
         engine_session_id: None,
         structured: None,
+        profile: None,
     };
     let dto = TerminalSessionDto::from(out);
     assert_eq!(dto.cell_kind, CellKind::Pty, "no descriptor ⇒ pty");
@@ -207,6 +209,7 @@ fn pty_launch_output_serialises_cellkind_pty_without_breaking_existing_keys() {
         assigned_conversation_id: None,
         engine_session_id: None,
         structured: None,
+        profile: None,
     };
     let v = serde_json::to_value(TerminalSessionDto::from(out)).unwrap();
     assert_eq!(v["sessionId"], sid.to_string());