fix(tmux): handle single-pane pane-state parsing

[code-yeongyu]

Summary

• Recreate closed PR fix(tmux): handle single-pane pane-state parsing #2365 on top of current dev for Linear issue 2241.
• Extract tmux list-panes stdout parsing into a dedicated pane-state-parser module.
• Keep single-pane parsing rules covered for empty trailing titles, CRLF output, and tab-containing titles.

Testing

• bun test src/features/tmux-subagent/pane-state-querier.test.ts
• bun run typecheck
• bun run build

---

Summary by cubic

Fixes tmux pane-state parsing for single-pane windows and normalizes list-panes output to prevent dropped panes and wrong layouts. Addresses Linear 2241 by introducing a dedicated parser used by the subagent.

• Bug Fixes

  • Accepts single-pane output when tmux omits the trailing title field.
  • Handles CRLF line endings without dropping panes.
  • Preserves tabs inside pane titles.

• Refactors

  • Extracted pane-state-parser to parse list-panes stdout and return window size plus panes.
  • Updated pane-state-querier to use the parser and simplified parsing logic with new tests.

^{Written for commit e1b59e3. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 3 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Auto-approved: The PR correctly refactors tmux parsing into a testable module, addressing specific edge cases like CRLF and single-pane output without changing the core window state logic.}