feat: enable tmux focus-events for focus tracking

[craftengineer]

Summary

• Add set -g focus-events on to tmux/tmux.conf so tmux forwards terminal focus-in/out events to programs running in panes.
• Fixes the tmux focus-events off warning shown by Claude Code; also benefits vim/neovim focus tracking. Purely additive and reversible.

Test plan

• tmux source-file ~/.tmux.conf then tmux show-options -g focus-events reports focus-events on
• The focus-events off warning no longer appears in a Claude Code pane inside tmux

Summary by CodeRabbit

• Chores
  • Enhanced tmux configuration to enable focus event reporting.

[coderabbitai]

Complex PR? Review this PR in Change Stack to move by importance, not file order.

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: dabca1c2-318f-4ff8-8f8c-f24414763485

📥 Commits

Reviewing files that changed from the base of the PR and between 44059fa and c012641.

📒 Files selected for processing (1)

• tmux/tmux.conf

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📝 Walkthrough

Walkthrough

Enables tmux focus event reporting by adding set -g focus-events on to the configuration file, allowing tmux to report window focus events to applications running inside tmux.

Changes

Tmux Focus Events

Layer / File(s)	Summary
Enable focus events tmux/tmux.conf	Adds set -g focus-events on configuration setting to enable tmux focus event reporting.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~1 minute

Poem

🐰 A single line, so clean and bright,
Focus events now burning light,
Tmux sees when windows come to play,
One small setting makes the day! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: enabling tmux focus-events for focus tracking, which matches the single line addition to tmux.conf.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/tmux-focus-events

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[Copilot]

Pull request overview

Enables tmux focus event forwarding so applications inside panes can detect terminal focus-in/out, addressing the focus-events off warning (e.g., from Claude Code) and improving editor focus tracking.

Changes:

• Add set -g focus-events on to the tmux global configuration.

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