fix: allow exact Chrome Web Store release version

[numbers-official]

Summary

This PR fixes the Chrome Web Store release workflow when the repository version is behind the already-published store version.

The Chrome Web Store currently has 1.2.0, but main still has 1.1.4. The existing workflow could only bump from the repository version:

• patch -> 1.1.5, still lower than Chrome Web Store
• minor -> 1.2.0, equal to Chrome Web Store and not uploadable
• major -> 2.0.0, too large for this release

Changes

• Add optional target_version workflow input for exact release versions, e.g. 1.2.1.
• Keep existing patch / minor / major behavior when target_version is empty.
• Allow scripts/bump-version.js to accept either a bump type or an exact x.y.z version.
• Reject non-incrementing target versions relative to the repository version.
• Sync version metadata across:
  • manifest.template.json
  • package.json
  • package-lock.json

Release Instructions

After this PR is merged, run Release to Chrome Web Store manually with:

• version_type: patch (ignored when target_version is set)
• target_version: 1.2.1

This will generate and upload extension version 1.2.1 without requiring an incorrect major bump.

Verification

• Tested exact bump to 1.2.1 in a temporary directory
• Tested subsequent patch bump still works
• Tested non-incrementing target versions are rejected
• npm run lint
• npx tsc --noEmit
• OAUTH_CLIENT_ID=test-client-id EXTENSION_KEY=test-extension-key npm run generate-manifest && npm run build
• GitHub CI passes

[numbers-official]

Re-reviewed PR 80. No regression issues found.\n\nChecked behavior:\n- exact target version works (tested 1.2.1)\n- existing patch bump still works after an exact version bump\n- non-incrementing target versions are rejected\n- package-lock.json root and package metadata are updated together with package.json and manifest.template.json\n- workflow passes user input through env vars before shell use\n\nVerification:\n- GitHub CI is green\n- npm run lint passes with existing warnings only\n- npx tsc --noEmit passes