docs: improve contributor setup and PR template

.github/pull_request_template.md

@@ -1,34 +1,29 @@
 ## Summary
 
-- What changed?
-- Why was it needed?
+<!-- Describe what changed and why. Link the related issue, for example: Closes #123. -->
 
-## Scope
+## Type of change
 
-- [ ] `training-py`
-- [ ] `nan-python-engineering-labs`
-- [ ] Both repos
+- [ ] Documentation
+- [ ] Bug fix
+- [ ] New or updated learning content
+- [ ] Repository tooling
+- [ ] Other
 
-## Validation
+## How Has This Been Tested?
 
-- [ ] `scripts/validate_all_modules.py`
-- [ ] `scripts/run_topic_tests.py <target>`
-- [ ] Relevant examples executed when applicable
+<!-- Check the commands you ran and replace TARGET with the relevant module or topic. -->
 
-Paste key outputs:
+- [ ] `uv run scripts/validate_all_modules.py`
+- [ ] `uv run scripts/validate_ci_gate.py`
+- [ ] `uv run scripts/run_topic_tests.py TARGET`
+- [ ] Manual validation (describe below)
 
-```text
-SUMMARY: ...
-```
+<!-- If automated validation does not apply, explain why and describe your manual checks. -->
 
 ## Checklist
 
-- [ ] Commit messages are in English
-- [ ] No TODO placeholders introduced
-- [ ] `exercise/exercise_01.py` remains English-only
-- [ ] No unrelated files were modified
-
-## Risks / Notes
-
-- Potential impact:
-- Follow-up tasks (if any):
+- [ ] I followed the contribution guidelines.
+- [ ] I kept the change focused and used English throughout.
+- [ ] I added or updated tests and documentation where applicable.
+- [ ] I did not introduce TODO placeholders or unrelated changes.

CONTRIBUTING.md

@@ -1,35 +1,68 @@
 # Contributing
 
-## Branches
+Thank you for helping improve Python Engineering Labs. Keep contributions focused,
+beginner-friendly, and written in English.
 
-- Work from `main` using short-lived feature branches.
-- Keep one logical change per branch.
+## Prerequisites
 
-## Commits
+- [Git](https://git-scm.com/)
+- Python 3.12 or newer
+- [uv](https://docs.astral.sh/uv/)
 
-- Use English commit messages.
-- Keep commits focused and small.
-- Avoid mixing infra and content changes in the same commit when possible.
+You can also use the repository's Dev Container. See
+[Getting Started](GETTING_STARTED.md) for the complete setup options.
 
-## Validation Before Commit
+## Local setup
 
-Run from repo root:
+Fork the repository on GitHub, then clone your fork:
 
 ```bash
+git clone https://github.com/YOUR_GITHUB_USERNAME/nan-python-engineering-labs.git
+cd nan-python-engineering-labs
+uv venv
+```
+
+Activate the virtual environment:
+
+```bash
+# macOS or Linux
 source .venv/bin/activate
-python scripts/validate_all_modules.py
-python scripts/run_topic_tests.py 01_python_fundamentals/advanced_strings
+
+# Windows PowerShell
+.venv\Scripts\Activate.ps1
 ```
 
-Or using `uv run`:
+Install the development dependencies:
+
+```bash
+uv pip install -e ".[dev]"
+pre-commit install
+```
+
+Install all optional dependencies with `uv pip install -e ".[all]"` when your
+change needs the full curriculum validation used in CI.
+
+## Validate your change
+
+Run the checks that match your change from the repository root:
 
 ```bash
 uv run scripts/validate_all_modules.py
+uv run scripts/validate_ci_gate.py
 uv run scripts/run_topic_tests.py 01_python_fundamentals/advanced_strings
 ```
 
-## Pull Requests
+Run all topic tests with `uv run scripts/run_topic_tests.py`. For documentation-only
+changes, preview the rendered Markdown and state in the pull request when automated
+tests do not apply.
+
+## Submit a pull request
+
+1. Create a short-lived branch from `main` for one logical change.
+1. Use focused commits with English messages.
+1. Push the branch to your fork and open a pull request against `main`.
+1. Complete the pull request template with the related issue, validation evidence,
+   and any risks or follow-up work.
 
-- Use the PR template.
-- Include scope, validation evidence, and risks.
-- Do not include unrelated changes.
+Before submitting, review the repository conventions in [AGENTS.md](AGENTS.md) and
+keep unrelated changes out of the pull request.