ci: add pre-commit hooks for code quality

[bugman-007]

Adds comprehensive pre-commit hooks for automated code quality checks:

Hooks added:

• shellcheck: Lints shell scripts (excludes SC1091, SC2034, SC2086)
• ruff: Python linting (E, F, W checks, ignores E501 line length)
• black: Python formatting (line-length=100)
• trailing-whitespace, end-of-file-fixer
• check-yaml, check-json

Also updates CONTRIBUTING.md with pre-commit setup instructions.

[bugman-007]

"⚠️ SHOULD MERGE AFTER #177 (formatting baseline)"

[Lightheartdevs]

Review: ⚠️ REQUEST CHANGES (minor)

This is a well-structured PR that makes sensible additions to the pre-commit configuration. One small fix needed.

What works well

• Hook selections are appropriate — shellcheck, ruff, black, trailing-whitespace, end-of-file-fixer, check-yaml, check-json
• All versions pinned — gitleaks v8.21.2, shellcheck v0.10.0.1, ruff v0.3.4, black 24.3.0, pre-commit-hooks v5.0.0
• shellcheck config is sensible — --severity=error only catches real bugs, exclusions (SC1091/SC2034/SC2086) are reasonable for this codebase
• ruff scoped correctly — ^dream-server/.*\.py$
• check-yaml --unsafe is necessary for docker-compose custom constructors
• CONTRIBUTING.md documentation is clear and helpful

Issue: Premature claim in CONTRIBUTING.md

The added text says:

All Python files have been formatted with black --line-length=100.

This is only true after PR #177 (black formatting baseline) merges. If #178 lands first, this statement is false. Either:

• Option A: Remove this sentence and add it in #177 instead
• Option B: Land #177 first, then rebase #178

The PR description already notes the dependency on #177, so this is likely just an ordering oversight.

Suggestions for follow-up (non-blocking)

• Consider centralizing ruff config in a pyproject.toml to keep CI and pre-commit in sync
• SC2086 exclusion is understandable for initial adoption but worth tracking for eventual removal
• end-of-file-fixer and trailing-whitespace will auto-modify files on first pre-commit run --all-files — expected but could surprise contributors

CI note

All failures are pre-existing on main. Lint Python with Ruff and Lint shell scripts both pass.

Small fix, then good to go. Nice work.

[bugman-007]

Addressed

Removed the premature claim about black formatting being complete. The statement "All Python files have been formatted with black --line-length=100" is only accurate after PR #177 merges.

The pre-commit hooks documentation remains intact - they will enforce black formatting going forward once #177 lands.

Changes: Removed 2 lines from CONTRIBUTING.md (commit 31b1918)

Kindly review this update, thanks.

[Lightheartdevs]

Closing — draft pre-commit hooks PR, depends on #177 which is also being closed. Please rebase and re-open when ready.