self-heal Claude panes stuck on an unconnectable session (T-147)

After session-id binding (T-146), a pane that attached (via new-session
-A) to a session created before the change — which has no --session-id,
so its transcript is under a different id — would wait forever for a
transcript that never appears. Same on any unconnectable session.

Before spawning, if no transcript exists for our deterministic session
id, kill the clide tmux session of that exact name so new-session
creates a clean one with our --session-id. This self-heals the stuck
state on next launch and makes clean-install/first-run robust.

Safe by construction: only clide's own session is killed — by its exact
clide-claude-<slug> name on the private -L clide socket (a terminal
claude never runs there) — and no transcript file is ever deleted. A
healthy session's transcript already exists, so re-attach continuity
(D-41) is preserved.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -120,6 +120,11 @@ heading, and (b) bumping `pubspec.yaml` `version:` in the same commit.
 
 ### Fixed
 
+- Claude pane no longer gets stuck on "Waiting for Claude…" when its
+  session can't be bound (T-147) — e.g. a session left over from before
+  session-id binding, or a fresh machine. It now retires that stale
+  clide session and starts a clean one. Only clide's own `-L clide`
+  sessions are touched (never a terminal Claude, never transcript files).
 - Secondary Claude tabs showed the primary's conversation instead of
   their own (T-146). Each pane now binds to its own session via
   `claude --session-id`, so concurrent sessions in one workspace stop