fix(chat): réattache persistante CLI custom et rendu tools/MCP/progress enrichi (#188)

Corrige la perte de session à la navigation: le démontage du CustomAgentChatView
appelait close_agent_session (destructeur) au lieu de simplement détacher le
transport. Désormais:

- nouvelle commande Tauri detach_agent_chat (+ ChatBridge::detach) qui libère le
  canal sans tuer la session ni le scrollback retenu; distinct de
  close_agent_session qui reste le close destructeur explicite;
- le frontend appelle detachAgentChat à l'unmount puis restore sa vue depuis un
  cache de session (turns + chunkCount) à la réattache;
- message « Reprise effectuée: N événements rattrapés… » quand la réattache
  rejoue plus de chunks que le cache local n'en avait conservé.

Enrichit le rendu tools/MCP/progress:

- ProgressSettler (chat bridge) émet un progress completed synthétique quand un
  spinner reste ouvert (nouvelle entité progress, chunk text/final/error): fini
  les spinners fantômes;
- les adapters claude/codex/opencode/openai_compat extraient un aperçu du
  payload (arguments/input/command/message/params) attaché au progress;
- bounded_reply_progress_preview (domain) garde les 4 premières lignes non
  vides, normalisation CR/LF;
- previewText (frontend) multiligne whitespace-pre-wrap, source/nativeEvent
  affichés sous le titre; suppression du flag settled et du Spinner inline
  devenus redondants (l'état est porté par le stage + le settler).

Tests: detach_agent_chat gateway (Tauri + mock), ProgressSettler, bornage
reply_progress, item_preview/tool_preview par adapter, réattache avec cache et
notice de rattrapage.

crates/app-tauri/src/chat.rs

@@ -34,7 +34,7 @@ use domain::ports::{
     ReplyEvent, ReplyProgress, ReplyProgressKind, ReplyProgressSource, ReplyProgressStage,
 };
 
-use crate::dto::ReplyChunk;
+use crate::dto::{ReplyChunk, ReplyProgressDto, ReplyProgressKindDto, ReplyProgressStageDto};
 use crate::stream::TauriChannelSink;
 
 /// Maximum number of recent chat chunks retained for transport reattach replay.
@@ -110,6 +110,13 @@ impl ChatBridge {
         self.inner.unregister(session);
     }
 
+    /// Detaches the current output channel while preserving the live session's
+    /// retained scrollback. This is the view-unmount path; it is intentionally
+    /// distinct from [`unregister`](Self::unregister), which is the real close.
+    pub fn detach(&self, session: &SessionId) {
+        self.inner.detach(session);
+    }
+
     /// Detaches a session's channel **only if** `gen` is still the current
     /// generation, leaving the scrollback intact. A pump calls this when its turn
     /// stream ends: if the session was re-attached meanwhile (newer generation),
@@ -136,6 +143,22 @@ impl ChatBridge {
         self.inner.send_output(session, chunk)
     }
 
+    /// Sends `chunk`, first completing any previous running progress entity when
+    /// the next chunk proves that another process/tool/MCP has taken over.
+    pub fn send_output_settled(
+        &self,
+        session: &SessionId,
+        settler: &mut ProgressSettler,
+        chunk: ReplyChunk,
+    ) -> bool {
+        let mut delivered = true;
+        if let Some(completed) = settler.before(&chunk) {
+            delivered &= self.send_output(session, completed);
+        }
+        let current_delivered = self.send_output(session, chunk);
+        delivered && current_delivered
+    }
+
     /// Number of currently-tracked sessions (handy for tests/diagnostics).
     #[must_use]
     pub fn active_sessions(&self) -> usize {
@@ -143,6 +166,86 @@ impl ChatBridge {
     }
 }
 
+/// Tracks one running progress entity for a chat stream and emits a synthetic
+/// `completed` update when subsequent activity makes the previous spinner stale.
+#[derive(Default)]
+pub struct ProgressSettler {
+    active: Option<ReplyProgressDto>,
+}
+
+impl ProgressSettler {
+    /// Completes the currently active progress entity, if any.
+    pub fn finish(&mut self) -> Option<ReplyChunk> {
+        self.complete_active()
+    }
+
+    fn before(&mut self, chunk: &ReplyChunk) -> Option<ReplyChunk> {
+        match chunk {
+            ReplyChunk::Progress { progress } => self.before_progress(progress),
+            ReplyChunk::TextDelta { .. }
+            | ReplyChunk::ToolActivity { .. }
+            | ReplyChunk::Final { .. }
+            | ReplyChunk::Error { .. }
+            | ReplyChunk::UserPrompt { .. } => self.complete_active(),
+        }
+    }
+
+    fn before_progress(&mut self, progress: &ReplyProgressDto) -> Option<ReplyChunk> {
+        if !is_settleable_progress(progress) {
+            return self.complete_active();
+        }
+        match progress.stage {
+            ReplyProgressStageDto::Started | ReplyProgressStageDto::Delta => {
+                let next_key = progress_entity_key(progress);
+                let previous = self.active.as_ref().and_then(progress_entity_key);
+                if previous.as_deref() == next_key.as_deref() {
+                    self.active = Some(progress.clone());
+                    None
+                } else {
+                    let completed = self.complete_active();
+                    self.active = Some(progress.clone());
+                    completed
+                }
+            }
+            ReplyProgressStageDto::Completed => {
+                let next_key = progress_entity_key(progress);
+                let previous = self.active.as_ref().and_then(progress_entity_key);
+                if previous.as_deref() == next_key.as_deref() {
+                    self.active = None;
+                }
+                None
+            }
+            ReplyProgressStageDto::Info => self.complete_active(),
+        }
+    }
+
+    fn complete_active(&mut self) -> Option<ReplyChunk> {
+        let mut progress = self.active.take()?;
+        progress.stage = ReplyProgressStageDto::Completed;
+        Some(ReplyChunk::Progress { progress })
+    }
+}
+
+fn is_settleable_progress(progress: &ReplyProgressDto) -> bool {
+    matches!(
+        progress.kind,
+        ReplyProgressKindDto::Tool | ReplyProgressKindDto::Mcp | ReplyProgressKindDto::Message
+    )
+}
+
+fn progress_entity_key(progress: &ReplyProgressDto) -> Option<String> {
+    if !is_settleable_progress(progress) {
+        return None;
+    }
+    let name = progress
+        .tool_name
+        .as_ref()
+        .filter(|name| !name.trim().is_empty())
+        .unwrap_or(&progress.label);
+    let name = name.trim().to_ascii_lowercase();
+    (!name.is_empty()).then(|| format!("{:?}:{name}", progress.kind))
+}
+
 fn reply_chunk_bytes(chunk: &ReplyChunk) -> usize {
     match chunk {
         ReplyChunk::UserPrompt { text, attachments } => {