Add CI workflows for automated addon packaging on PRs and releases

[Copilot]

Automates browser extension packaging for pull requests and releases. PRs get development builds with "IN-DEV" version; releases get properly versioned builds from the release tag.

Changes

• PR Workflow (.github/workflows/pr-build.yml)

  • Packs src/ directory to zip on PR open/update
  • Uploads artifact with 30-day retention
  • Posts comment with download link and installation instructions
  • Deduplicates bot comments on subsequent pushes

• Release Workflow (.github/workflows/release-build.yml)

  • Extracts version from release tag (strips v prefix)
  • Injects version into manifest.json, replacing "IN-DEV"
  • Packs and attaches versioned zip to release

• Manifest Version (src/manifest.json)

  • Changed from "2.1" to "IN-DEV" for development builds
  • Only release builds get numeric versions injected

Example Usage

Create release with tag v2.2.0:

gh release create v2.2.0

Workflow automatically:

1. Updates manifest: "version": "IN-DEV" → "version": "2.2.0"
2. Creates dom-time-machine-v2.2.0.zip
3. Attaches to release

Note: "IN-DEV" may fail browser extension validation for local development. Use numeric version (e.g., "0.0.0") if needed for manual testing.

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[github-actions]

🎉 Addon Build Complete

The addon has been successfully built for this PR!

Version: IN-DEV
Build: #21435343716

You can download the built addon from the artifacts section of the workflow run.

Installation Instructions

1. Download the artifact from the workflow run
2. Extract the zip file
3. Load the extension in your browser:
   • Firefox: Navigate to about:debugging#/runtime/this-firefox, click "Load Temporary Add-on", and select the manifest.json
   • Chrome: Navigate to chrome://extensions, enable "Developer mode", click "Load unpacked", and select the extracted folder