refactor: pane-centric state handling redesign

[boxp]

Summary

• Use pane-id as the primary key for the sessions store instead of session-id, eliminating duplicate entries when the same pane runs multiple sessions
• Remove all supersede logic (supersede-key, supersede-old-sessions, close-dup-pane-sessions, etc.) which is no longer needed with pane-id keying
• Remove SESSION column from TUI table/card views, clean up dead code (truncate, list-pane-cwds, unused parameters)
• Deduplicate capturable-statuses to single source in store.clj, remove redundant ensure-state-dir! calls, make with-file-lock private

Test plan

• make ci passes (format-check + lint + test)
• Verify same pane-id updates produce single entry
• Verify different pane-ids produce separate entries
• Verify session-id does not appear in TUI output
• Verify closed session reactivation works correctly
• Verify non-tmux sessions fall back to session-id as key

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Clear stale last-message when session-id changes

With pane-id now used as the primary key, update-session! merges new events into the previous pane record even when the pane has started a different session-id. Because many start/progress events intentionally omit :last-message, the old session’s message is retained and shown for the new session, which produces incorrect UI state after pane reuse. This needs a reset path (e.g., when incoming :session-id differs from stored :session-id) before merging.

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[chatgpt-codex-connector]

Migrate legacy session-id entries on pane-key writes

This change writes tmux updates under pane-id keys, but existing state files from the previous model can still contain active entries keyed by session-id; writing the new pane key here leaves the old key untouched, so both records remain active for the same pane until it dies. Since duplicate-pane cleanup was removed in this commit, upgraded users can see duplicate live rows and duplicated refresh updates unless the legacy key is remapped or removed when pane-keyed writes occur.

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