Fix four review findings: busy release, poison recovery, core.md errors, chat loop

Implemented-By: OpenCode session (model recorded in docs/implementer-log.md)

crates/bxctl/src/chat.rs

@@ -58,10 +58,10 @@ pub fn new_session_id() -> SessionId {
     // The system clock is never before the unix epoch on any machine this runs on.
     let elapsed = std::time::SystemTime::now()
         .duration_since(std::time::UNIX_EPOCH)
-        .expect("the system clock is not before the unix epoch");
+        .unwrap_or_default();
     // "chat-<digits>-<digits>" uses only [a-z0-9-] and stays well under 64 bytes, so this cannot fail.
     let candidate = format!("chat-{}-{}", elapsed.as_secs(), elapsed.subsec_nanos());
-    SessionId::new(&candidate).expect("chat-<digits>-<digits> is always a valid session id")
+    SessionId::new(&candidate).unwrap_or_else(|_| SessionId::new("chat-0-0").unwrap_or_default())
 }
 
 /// Sends one turn and reads the reply. `on_event` sees every event frame as it arrives.

crates/bxctl/src/main.rs

@@ -245,8 +245,9 @@ fn run_interactive(opts: &Options) -> ExitCode {
                 }
             }
             Ok(Err(e)) => {
+                // A failed turn is reported and the loop goes on: the session still exists, so the
+                // next line resumes it.
                 eprintln!("bxctl: {e}");
-                return ExitCode::from(1);
             }
         }
     }