ci: release-please automation for GitHub Releases + npm publish

[mrgoonie]

Summary

• Adds release-please automation driven by conventional commits on main
• Opens/updates a Release PR that bumps version in packages/cli/package.json + generates CHANGELOG.md
• On Release PR merge → creates git tag, GitHub Release, then auto-publishes CLI to npm
• Manifest seeded at current CLI version 0.1.4 (next release will bump from there)

How it works

1. Merge feature commits to main using conventional commits (feat:, fix:, feat!: for breaking)
2. release-please bot opens a Release PR titled e.g. chore(main): release f2u-cli 0.1.5
3. Review + merge the Release PR
4. Workflow re-runs, detects release → runs pnpm build + pnpm publish --access public
5. GitHub Release + npm package are live

Prerequisites (one-time setup by maintainer)

• Add NPM_TOKEN secret in repo Settings → Secrets → Actions (npm automation token, `publish` scope)
• Ensure default GITHUB_TOKEN has write permissions (Settings → Actions → General → Workflow permissions → Read and write)

Version bump rules

Commit prefix	Bump
`fix:`	patch (0.1.4 → 0.1.5)
`feat:`	minor (0.1.4 → 0.2.0) — but while pre-1.0, kept as patch bump via `bump-minor-pre-major`
`feat!:` / `BREAKING CHANGE:`	major
`chore:`, `docs:`, `ci:`, `refactor:`	no release

Test plan

• Merge this PR → release-please should open a Release PR for any unreleased commits since 0.1.4 (if none found with release-triggering prefix, no PR opens — expected)
• Create a `fix:` commit on main → Release PR opens
• Merge Release PR → verify tag `f2u-cli-v0.1.5`, GitHub Release, and `npm view f2u-cli version` updates