fix(agent): ne câbler le PTY qu'en lancement brut, pas structuré — §17.4/§17.6

Un launch structuré route vers une AgentSession enregistrée dans
StructuredSessions ; son id n'est jamais un PTY vivant. Câbler le bridge PTY
appelait subscribe_output avec un id inconnu de l'adapter → NotFound
("pty handle not found"), faisant échouer tout lancement d'agent structuré.
On ne pompe les octets que sur le chemin PTY brut (structured: None).

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

crates/app-tauri/src/commands.rs

@@ -1064,6 +1064,14 @@ pub async fn launch_agent(
 
     let session_id = output.session.id;
 
+    // §17.4/§17.6: a structured launch routes to an `AgentSession`, registered
+    // **only** in `StructuredSessions` — its id is never a live PTY. Such a cell is
+    // a chat view driven by `agent_send`/`reattach_agent_chat`, not by xterm bytes,
+    // so we must NOT wire it to the PTY bridge. Doing so would call
+    // `subscribe_output` with an id the PTY adapter has never seen → `NotFound`
+    // ("process error: pty handle not found"), failing every structured agent
+    // launch. Only the raw-PTY path (`structured: None`) gets the byte pump.
+    if output.structured.is_none() {
         // Register the xterm output channel for this session.
         let gen = state.pty_bridge.register(session_id, on_output);
 
@@ -1088,6 +1096,7 @@ pub async fn launch_agent(
                 return Err(ErrorDto::from(AppError::from(e)));
             }
         }
+    }
 
     Ok(TerminalSessionDto::from(output))
 }