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

[code-yeongyu]

Summary

• Extract tmux list-panes stdout parsing into a dedicated pane state parser.
• Accept pane rows with 8 mandatory fields so single-pane sessions still parse when pane_title is empty.
• Normalize CRLF line endings and add coverage for empty titles, CRLF output, and tab-containing titles.

Testing

• bun test src/features/tmux-subagent/
• bun run typecheck
• bun run build

---

Summary by cubic

Fixes tmux pane parsing for single-pane sessions and CRLF output by introducing a dedicated parser, preventing window state failures when pane_title is empty. Addresses Linear issue 2241.

• Bug Fixes

  • Accept pane rows with 8 mandatory fields (no trailing title) so single-pane sessions parse.
  • Normalize CRLF line endings to avoid dropping panes.
  • Preserve tabs inside pane titles.

• Refactors

  • Extracted tmux list-panes parsing into pane-state-parser and integrated it into pane-state-querier.
  • Added unit tests for empty titles, CRLF output, and titles containing tabs.

^{Written for commit 8b71559. 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 refactors tmux parsing logic into a well-tested dedicated parser, specifically fixing a bug where single-pane sessions were ignored. The logic is robust and addresses CRLF issues.}