Initial commit: Share-as-QR Firefox extension with bun build

MV3 WebExtension that turns the active tab's URL into a scannable QR
code via a toolbar popup. The popup runs locally — no network requests.

Build pipeline: `bun build` bundles popup.js + the vendored
kazuhikoarase/qrcode-generator (MIT, pinned to 83b7e8f) into a single
~23 KB minified ESM file under dist/. web-ext operates on dist/, so
the packaged zip contains only what actually ships (~28 KB).

Scripts:
- bun run build    — bundle + copy assets into dist/
- bun run lint     — build + web-ext lint (0 errors / 0 warnings)
- bun run package  — build + produce a signable .zip
- bun run start    — build + launch Firefox with the extension loaded

Tracks dogcat epic firefox-share-as-qr-35mw and its 5 child tasks
(scaffold, vendor lib, popup UI, icons, README).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,8 @@
+.dogcats/config.local.toml
+.dogcats/.issues.lock
+.claude/settings.local.json
+web-ext-artifacts/
+node_modules/
+dist/
+bun.lockb
+bun.lock