chore: add pre-commit hook to auto-format and lint staged .ts files

[t2tx]

Summary

Adds a pre-commit lefthook job that runs prettier --write + eslint --fix on staged *.ts files and re-stages them.

Why

• Commits are formatted/linted on the way in, so they're less likely to fail the pre-push verify (format:check / lint).
• pre-push (pnpm verify) is unchanged.

Verification

• lefthook dump parses the config; lefthook run pre-commit skips when no *.ts is staged (glob works).
• No functional change — tooling only, so no version bump.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Chores
  • Added automated pre-commit checks for TypeScript code formatting and linting.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 43f3a7b1-06ae-488c-8a11-19c922bc4386

📥 Commits

Reviewing files that changed from the base of the PR and between 357885e and d95beb2.

📒 Files selected for processing (1)

• lefthook.yml

🚧 Files skipped from review as they are similar to previous changes (1)

• lefthook.yml

---

Walkthrough

A pre-commit hook section is added to lefthook.yml with two jobs: format (runs pnpm prettier --write on staged *.ts files and re-stages them) and lint (runs pnpm eslint --fix on staged *.ts files and re-stages them). The existing pre-push configuration is unchanged.

Changes

Pre-commit Lefthook Configuration

Layer / File(s)	Summary
Pre-commit format and lint jobs lefthook.yml	Adds a pre-commit section with format and lint jobs that run pnpm prettier --write and pnpm eslint --fix respectively on staged *.ts files, followed by git add {staged_files} to persist auto-fixes.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

🚥 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 accurately summarizes the main change: adding a pre-commit hook for auto-formatting and linting TypeScript files. It is concise, clear, and directly related to the primary purpose of the pull request.
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.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch chore/lefthook-precommit

---

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[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@lefthook.yml`:
- Line 4: The glob patterns in the lefthook.yml file for both the format and
lint jobs use `*.ts` which only matches TypeScript files in the root directory
and does not match files in subdirectories like src/. Update both glob pattern
declarations (in the format job at line 4 and in the lint job at line 7) from
`*.ts` to `**/*.ts` to match TypeScript files at any depth in the directory
structure, ensuring that staged files in src/ subdirectories are properly
processed by the pre-commit hooks.
- Around line 1-9: The glob patterns in both the format and lint jobs under
pre-commit are too restrictive and only match TypeScript files in the repository
root. Update the glob pattern from "*.ts" to "**/*.ts" (or "src/**/*.ts" if you
want to be more specific) in both the format job and lint job to ensure that
TypeScript files in subdirectories like src/ are also matched and processed
during the pre-commit hook.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 5386c64b-f1a9-4a66-98ac-a6ae4ae4e589

📥 Commits

Reviewing files that changed from the base of the PR and between 354ae1e and 357885e.

📒 Files selected for processing (1)

• lefthook.yml

[t2tx]

@coderabbitai Updated both globs to **/*.ts.

A note for the record: I tested the original *.ts against a staged src/format.ts under lefthook 2.1.9 and it did match (format + eslint ran on it) — lefthook applies the glob per staged file name, so root-only matching doesn't apply here. So this wasn't a behavior fix. That said, **/*.ts makes the "any depth" intent explicit and is robust to future glob_matcher changes, so I've adopted it.

[coderabbitai]

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@t2tx: Thanks for the update and the detailed clarification! Good to know that lefthook 2.1.9 applies globs against the bare filename rather than the full path, so *.ts was already matching src/format.ts correctly. The switch to **/*.ts still reads better as a statement of intent and guards against any future glob_matcher changes, so it's a net improvement even if it wasn't a functional fix.

---

✏️ Learnings added

Learnt from: t2tx
URL: https://github.com/t2tx/iris/pull/21

Timestamp: 2026-06-22T01:31:25.151Z
Learning: In lefthook 2.1.9, the `glob` filter in a job configuration is applied against each staged file's **basename** (not the full path). This means `*.ts` already matches files in subdirectories (e.g., `src/format.ts`), so root-only matching is not a concern. Using `**/*.ts` is still preferred for explicit "any depth" intent and robustness against future `glob_matcher` changes, but switching from `*.ts` to `**/*.ts` in a lefthook configuration is a clarity improvement, not a behavior fix.

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