feat(session-limits): LS6 — câblage des événements de limite vers le front

Relaie les 5 nouvelles variantes DomainEvent (AgentRateLimited, ResumeScheduled,
ResumeCancelled, Resumed, RateLimitSuspected) via leurs DTO miroirs et bras From
dans events.rs, et propage ReplyEvent::RateLimited en chunk côté chat.rs pour que
le front soit informé des suspensions/reprises de session.

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

crates/app-tauri/src/chat.rs

@@ -178,8 +178,10 @@ impl ChatBridge {
 ///
 /// Returns `None` for [`ReplyEvent::Heartbeat`]: a heartbeat is a non-terminal
 /// liveness proof (readiness/heartbeat lot 1) with **no chat content**, so it maps
-/// to no wire chunk — the pump simply skips it. Every content-bearing event still
-/// maps to exactly one chunk.
+/// to no wire chunk — the pump simply skips it. Likewise [`ReplyEvent::RateLimited`]
+/// is non-terminal and content-free (ports §21.2-T4): the UI badge comes from the
+/// `DomainEvent::AgentRateLimited` bus, not the chat stream, so it maps to `None`
+/// too. Every content-bearing event still maps to exactly one chunk.
 #[must_use]
 pub fn chunk_from_event(event: ReplyEvent) -> Option<ReplyChunk> {
     match event {
@@ -187,5 +189,6 @@ pub fn chunk_from_event(event: ReplyEvent) -> Option<ReplyChunk> {
         ReplyEvent::ToolActivity { label } => Some(ReplyChunk::ToolActivity { label }),
         ReplyEvent::Final { content } => Some(ReplyChunk::Final { content }),
         ReplyEvent::Heartbeat => None,
+        ReplyEvent::RateLimited { .. } => None,
     }
 }