feat(orchestrator): backstop no-reply du rendez-vous inter-agents

Remédiation du wedge persistant après échec live du fix Finding A (77e62e5).
Détecte la fin de tour d'un agent sollicité qui n'a pas appelé idea_reply et
débloque l'agent demandeur au lieu de le laisser en attente indéfinie.

Ajoute le suivi de tour côté inspector Claude (claude_turn_watcher) et la
résolution des chemins de session (claude_paths), câblés dans le rendez-vous
idea_ask_agent ⇄ idea_reply.

Build workspace vert, suite complète verte, zéro warning.
Backstop NON prouvé levé en live : merge develop interdit tant que la levée
du wedge n'est pas validée en conditions réelles.

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

crates/domain/src/ports.rs

@@ -1305,6 +1305,46 @@ pub trait SessionInspector: Send + Sync {
     ) -> Result<ConversationDetails, InspectError>;
 }
 
+/// Callback fired **once per detected turn end** by a [`TurnWatcher`].
+///
+/// Invoked from the watcher's own polling task (never while holding a lock), so the
+/// composition root can safely route it to
+/// [`crate::input::InputMediator::turn_ended`] for the given agent.
+pub type OnTurnEnd = Arc<dyn Fn(AgentId) + Send + Sync>;
+
+/// Opaque handle to a live [`TurnWatcher::watch`]. **Dropping it stops the watch**
+/// (the adapter's polling task must observe the drop and cease firing, idempotently).
+pub trait TurnWatchHandle: Send + Sync {}
+
+/// Observes an agent's **end-of-turn** signal from its on-disk transcript, replacing
+/// the dead PTY prompt-ready sniff as the turn-end authority (rendez-vous no-reply
+/// backstop). Model-specific: an adapter watches the CLI's transcript shape (e.g. the
+/// Claude `turn_duration` record) and fires [`OnTurnEnd`] each time a turn completes.
+///
+/// Pure port (no async, no I/O in the trait): the adapter owns its polling task. The
+/// composition root arms one watch per **live agent session** (keyed on `cwd`, the
+/// agent's isolated run dir) and drops the handle on close/exit.
+pub trait TurnWatcher: Send + Sync {
+    /// Whether this watcher knows how to read turn ends for the given profile
+    /// (mirrors [`SessionInspector::supports`] — e.g. recognising `CLAUDE.md`).
+    fn supports(&self, profile: &AgentProfile) -> bool;
+
+    /// Arms a watch over `agent`'s transcript under `cwd` (its run dir). The adapter
+    /// captures a **baseline** of turn ends already present at arm time and fires
+    /// `on_turn_end(agent)` only on increments **above** that baseline (so a
+    /// pre-existing transcript — relaunch / background wake — never triggers a phantom
+    /// turn end). `conversation_id` is an optional diagnostic label only — it is **not**
+    /// the file key (the transcript stem is the engine session id, unknown at cold
+    /// start). Returns a [`TurnWatchHandle`]; dropping it stops the watch.
+    fn watch(
+        &self,
+        agent: AgentId,
+        conversation_id: Option<String>,
+        cwd: ProjectPath,
+        on_turn_end: OnTurnEnd,
+    ) -> Box<dyn TurnWatchHandle>;
+}
+
 /// Publish/subscribe domain events. Synchronous, in-process.
 pub trait EventBus: Send + Sync {
     /// Publishes an event.