ci: automate semantic versioning, changelog and npm release with Release Please

[Zhang-JiahangH]

Motivation

• Remove manual, hard-coded version bumps and enable automated patch/minor releases driven by conventional commits so routine releases do not require manual version selection.
• Prevent publishing the wrong package version by validating git tag vs packages/react/package.json before npm publish.

Description

• Add Release Please workflow (.github/workflows/release-please.yml) that runs googleapis/release-please-action@v4 to create/update release PRs from Conventional Commits.
• Add release-please-config.json to declare packages/react as the releasable package and .release-please-manifest.json to store the repository-managed package baseline version (0.1.2).
• Update publish workflow (.github/workflows/release.yml) to use pnpm install --frozen-lockfile and to validate the vX.Y.Z tag against packages/react/package.json before running the npm publish step.
• Bump packages/react/package.json to 0.1.2 and update CHANGELOG.md and README.md to document the automated versioning and SemVer rules (fix: -> patch, feat: -> minor, feat!:/BREAKING CHANGE: -> major).

Testing

• Executed pnpm install --frozen-lockfile successfully.
• Executed pnpm lint && pnpm build && pnpm typecheck && pnpm test and all steps completed successfully.

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Codex Task