feat(session-limits): LS4 — service application + réconciliation T4

Orchestre la détection et la reprise au niveau application :
- session_limit.rs (nouveau) : SessionLimitService + port AgentResumer +
  const RESUME_PROMPT.
- structured.rs : réconciliation T4 — enum TurnOutcome +
  drain_with_readiness_outcome ; signatures historiques préservées.
- agent/mod.rs + lib.rs : modules et re-exports.

Tests QA (nouveaux) : tests/session_limit_service.rs (9) +
tests/session_limit_t4.rs (7).
`cargo test -p application` = tous binaires verts / 0 failed (16 nouveaux),
zéro régression (drain_with_readiness_lot1 7/7, send_blocking_d1 9/9) ;
builds domaine+infra+application 0 warning.

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

crates/application/src/agent/mod.rs

@@ -10,13 +10,17 @@ mod catalogue;
 mod inspect;
 mod lifecycle;
 mod resume;
+mod session_limit;
 mod structured;
 mod usecases;
 
 pub(crate) use lifecycle::unique_md_path;
 pub(crate) use lifecycle::ReattachDecision;
 
-pub use structured::{drain_with_readiness, send_blocking};
+pub use session_limit::{AgentResumer, SessionLimitService, RESUME_PROMPT};
+pub use structured::{
+    drain_with_readiness, drain_with_readiness_outcome, send_blocking, TurnOutcome,
+};
 
 pub use catalogue::{reference_profile_id, reference_profiles, selectable_reference_profiles};
 pub use inspect::{InspectConversation, InspectConversationInput, InspectConversationOutput};