chore: add Claude Code configuration

Add AI assistant configuration for consistent development:

- CLAUDE.md: project overview and workflow
- rules/coding.md: YAML, bash, security, and documentation standards
- rules/dutch-communication.md: language preferences and commit conventions
- skills/: lint, release, and validate-action commands

Author: robbertbos

.claude/CLAUDE.md

@@ -0,0 +1,23 @@
+# ZAD Actions
+
+GitHub Actions for deploying to ZAD (Zelfservice voor Applicatie Deployment) at Rijks ICT Gilde.
+
+## Tech Stack
+
+- **GitHub Actions**: Composite actions (`runs.using: composite`)
+- **Bash**: Scripts in action steps
+- **curl**: ZAD API calls
+- **gh CLI**: GitHub API interactions
+
+## Workflow
+
+1. Edit `action.yml` files
+2. Run `pre-commit run --all-files`
+3. Update README.md if inputs/outputs changed
+4. Update CHANGELOG.md
+5. Create PR with conventional commit
+
+## Versioning
+
+- `v1.0.0` - exact version
+- `v1` - major tag (users reference this)

.claude/rules/coding.md

@@ -0,0 +1,52 @@
+# Coding Rules
+
+## YAML (action.yml)
+
+- 2-space indentation
+- Quote strings in `with:` blocks
+- Use `|` for multi-line bash
+- Always set `required: true/false` and `description` for inputs/outputs
+
+## Bash
+
+Validate inputs BEFORE logging (prevents injection):
+```bash
+if ! echo "$INPUT" | grep -qE '^[a-zA-Z0-9._-]+$'; then
+  echo "Error: invalid characters"; exit 1
+fi
+echo "Processing: $INPUT"
+```
+
+Best-effort pattern (don't fail entire action on one step):
+```bash
+if some_command; then
+  echo "deleted=true" >> "$GITHUB_OUTPUT"
+else
+  echo "::warning::Step failed but continuing"
+  echo "deleted=false" >> "$GITHUB_OUTPUT"
+fi
+```
+
+HTTP response handling:
+```bash
+RESPONSE=$(curl -s -w "\n%{http_code}" --max-time 60 "$URL")
+HTTP_CODE=$(echo "$RESPONSE" | tail -n1)
+BODY=$(echo "$RESPONSE" | sed '$d')
+```
+
+## Security
+
+- Never log secrets
+- Use env vars for sensitive data, not args
+- Always `--max-time` on curl
+- Quote all `"$VAR"` expansions
+
+## Commits
+
+Before committing, always update CHANGELOG.md under [Unreleased].
+
+## Documentation
+
+When changing action.yml inputs/outputs, update the README.md tables:
+- Inputs: Name | Required | Default | Description
+- Outputs: Name | Description

.claude/rules/dutch-communication.md

@@ -0,0 +1,16 @@
+# Communication
+
+Respond in Dutch when user writes Dutch. Code/commits stay English.
+
+## Commits
+
+Conventional commits in English:
+```
+feat(cleanup): add PR comment deletion
+
+Context explaining the why, not the what.
+```
+
+Prefixes: `feat:` `fix:` `docs:` `chore:` `refactor:` `test:`
+
+**Never add `Co-Authored-By: Claude` or any AI attribution to commits.**

.claude/skills/lint.md

@@ -0,0 +1,9 @@
+# /lint
+
+Run `pre-commit run --all-files`
+
+If not installed:
+```bash
+uv tool install pre-commit
+pre-commit install
+```

.claude/skills/release.md

@@ -0,0 +1,15 @@
+# /release <version>
+
+1. Verify CHANGELOG.md has entry for version
+2. Extract release notes from CHANGELOG.md (section for this version)
+3. Create and push tags:
+```bash
+git tag -a v<version> -m "Release v<version>"
+git push origin v<version>
+git tag -fa v<major> -m "Update v<major> to v<version>"
+git push origin v<major> --force
+```
+4. Create release with notes from changelog:
+```bash
+gh release create v<version> --title "v<version>" --notes "<notes from changelog>"
+```

.claude/skills/validate-action.md

@@ -0,0 +1,9 @@
+# /validate-action <action>
+
+Validate `deploy` or `cleanup` action.yml:
+
+1. Check required fields: name, description, branding, input/output descriptions
+2. Verify `${{ inputs.* }}` references exist
+3. Verify output values reference valid step IDs
+4. Check README.md matches action.yml
+5. Report issues with line numbers

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `.editorconfig` for consistent editor formatting
 - `.github/dependabot.yml` for automated GitHub Actions updates
 - `.gitignore` for local settings and Claude plans
+- `.claude/` configuration for AI assistant (coding rules, skills, workflow)
 - **deploy** action: PR commenting feature
   - Automatically post/update a comment on PRs with the deployment URL
   - New inputs: `comment-on-pr`, `github-token`, `comment-header`