chore(skills): add release-please skill for triggering versioned releases (#129)

Add a new Claude Code skill that automates the release-please workflow:

- Create .claude/skills/release-please/SKILL.md with instructions for
  triggering a specific version release via Release-As commit trailer
- Update CLAUDE.md with Available Skills section documenting the new skill

Usage: /release-please <version> (e.g., /release-please 2.3.0)

The skill creates a branch, commits with Release-As trailer, and opens
a PR that triggers release-please to create a release for that version.

Author: ryoppippi

.claude/skills/release-please/SKILL.md

@@ -0,0 +1,51 @@
+# Release Please Trigger
+
+Trigger a release-please PR for a specific version.
+
+## Usage
+
+```
+/release-please <version>
+```
+
+## Examples
+
+```
+/release-please 2.3.0
+/release-please 3.0.0
+```
+
+## Instructions
+
+When this skill is invoked with a version argument:
+
+1. **Validate the version format**: Ensure the version follows semantic versioning (X.Y.Z format)
+
+2. **Create a new branch**: Create a branch named `chore/trigger-release-<version>`
+
+   ```bash
+   git switch -c chore/trigger-release-<version>
+   ```
+
+3. **Create an empty commit with Release-As trailer**: The commit message must include the `Release-As: <version>` trailer to trigger release-please
+
+   ```bash
+   git commit --allow-empty -m "chore: trigger release <version>
+
+   Release-As: <version>"
+   ```
+
+4. **Push the branch and create a PR**:
+
+   ```bash
+   git push -u origin chore/trigger-release-<version>
+   gh pr create --title "chore: trigger release <version>" --body "Trigger release-please to create version <version>."
+   ```
+
+5. **Report the PR URL** to the user
+
+## Notes
+
+- The `Release-As` trailer in the commit message tells release-please to use that specific version
+- Once the PR is merged to main, release-please will automatically create a release PR with the specified version
+- The release PR will update CHANGELOG.md, version files, and create a GitHub release when merged

CLAUDE.md

@@ -8,6 +8,12 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 - **Skills** (`.claude/skills/`): Manually invoked for specific integrations.
 - **Cursor rules** (`.cursor/rules/`): Symlinks to `.claude/rules/` for consistency.
 
+## Available Skills
+
+| Skill              | Usage                       | Description                                        |
+| ------------------ | --------------------------- | -------------------------------------------------- |
+| **release-please** | `/release-please <version>` | Trigger a release-please PR for a specific version |
+
 ## Available Rules
 
 | Rule                         | Applies To          | Description                                        |