Add pre-commit with formatting.

.pre-commit-config.yaml

@@ -0,0 +1,7 @@
+repos:
+  - repo: https://github.com/astral-sh/ruff-pre-commit
+    rev: v0.15.14
+    hooks:
+      - id: ruff-check
+        args: [--fix]
+      - id: ruff-format

CONTRIBUTING.md

@@ -55,3 +55,25 @@ Use your real name (sorry, no pseudonyms or anonymous contributions.)
 
 If you set your `user.name` and `user.email` git configs, you can sign your
 commit automatically with `git commit -s`.
+
+### Run pre-commit locally
+
+This repository uses pre-commit to run Ruff checks before commits.
+
+Set it up once:
+
+```bash
+uv sync --dev
+uv run pre-commit install
+```
+
+Run hooks on all files:
+
+```bash
+uv run pre-commit run --all-files
+```
+
+Current hooks:
+
+- `ruff check --fix`
+- `ruff format`

pyproject.toml

@@ -33,6 +33,7 @@ xe-forge-skill = "xe_forge.skills:main"
 
 [dependency-groups]
 dev = [
+  "pre-commit>=4.6.0",
   "pytest>=7.0.0",
   "pytest-cov>=4.0.0",
   "ruff>=0.9.0",