feat(HAI-081): add changesets-based automated versioning and release workflow

- Install and configure @changesets/cli with commit/access settings
- Create version PR workflow (.github/workflows/version.yml) for automated version bumps
- Update existing release and test-release workflows with version validation
- Add example changeset and version tests for CI verification
- Add RELEASING.md guide and update README with versioning documentation

RELEASING.md

@@ -0,0 +1,62 @@
+# Releasing
+
+This project uses [changesets](https://github.com/changesets/changesets) for automated versioning and release management.
+
+## How it works
+
+### 1. Add a changeset
+
+When you make a change that should be included in a release, add a changeset:
+
+```bash
+pnpm changeset
+```
+
+This will prompt you to:
+- Select which packages are affected
+- Choose the semver bump type (patch, minor, major)
+- Write a summary of the change
+
+A markdown file will be created in the `.changeset/` directory. Commit this file along with your code changes.
+
+### 2. Version PR is created automatically
+
+When changesets are merged to `main`, a GitHub Actions workflow automatically opens (or updates) a **"Version Packages"** pull request. This PR:
+
+- Consumes all pending changeset files
+- Bumps package versions according to the changeset declarations
+- Generates/updates `CHANGELOG.md` files for affected packages
+
+### 3. Merge the Version PR to release
+
+When you merge the Version Packages PR:
+
+- The workflow detects that all changesets have been consumed
+- It creates a git tag `v{version}` based on the `hai` CLI package version
+- The tag push triggers the existing release workflow (`.github/workflows/release.yml`)
+- The release workflow builds binaries and creates a GitHub Release
+
+## Manual release (fallback)
+
+If you need to release manually, you can still push a version tag directly:
+
+```bash
+git tag v0.2.0
+git push origin v0.2.0
+```
+
+This will trigger the release workflow. Note: the workflow validates that the tag version matches `packages/cli/package.json`, so make sure they're in sync.
+
+## Available scripts
+
+| Script | Description |
+|--------|-------------|
+| `pnpm changeset` | Add a new changeset |
+| `pnpm changeset status` | Check pending changesets |
+| `pnpm release:version` | Apply changesets and bump versions (used by CI) |
+
+## Tips
+
+- Every user-facing change should have a changeset — CI will remind you if one is missing
+- You can add multiple changesets per PR if you're making changes to multiple packages
+- Changeset files are automatically deleted when versions are bumped