docs: add CLAUDE.md for Claude Code guidance

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Repository Overview
+
+This repository contains reusable Gitea Actions workflows for Unbound Software repositories. These workflows are called from other repositories using Gitea's `workflow_call` trigger.
+
+## Architecture
+
+- **Location**: Workflows are stored in `.gitea/workflows/` (not `.github/workflows/`)
+- **Platform**: Gitea Actions (compatible with GitHub Actions syntax but runs on Gitea)
+- **Base images**: Uses pinned Alpine and git-cliff images with SHA256 digests for reproducibility
+
+### Release.yml Workflow
+
+The main workflow automates semantic versioning releases using git-cliff for changelog generation:
+
+1. **preconditions**: Validates release token exists at `/runner-secrets/release-token`
+2. **changelog**: Generates changelog, determines version bump, checks for changes
+3. **handle-pr**: Creates/updates a `next-release` branch and PR with CHANGELOG.md and .version
+4. **prepare-release**: Prepares release artifacts when triggered
+5. **create-release** or **create-tag**: Creates Gitea release or tag based on `tag_only` input
+
+Version tracking uses a `.version` JSON file containing `{"version":"vX.Y.Z"}`.
+
+## Development Notes
+
+- No build/test commands exist - this is a workflow-only repository
+- Workflows use Gitea API directly via curl (not gh CLI)
+- Authentication reads from file-based token at `/runner-secrets/release-token`
+- Container images should include SHA256 digests for security