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>

manifest.json

@@ -0,0 +1,34 @@
+{
+  "manifest_version": 3,
+  "name": "Share as QR",
+  "version": "0.1.0",
+  "description": "Share the current tab's URL as a scannable QR code.",
+  "browser_specific_settings": {
+    "gecko": {
+      "id": "share-as-qr@olemd.local",
+      "strict_min_version": "142.0",
+      "data_collection_permissions": {
+        "required": ["none"]
+      }
+    }
+  },
+  "permissions": ["activeTab", "clipboardWrite"],
+  "action": {
+    "default_title": "Share page as QR code",
+    "default_popup": "popup/popup.html",
+    "default_icon": {
+      "16": "icons/icon.svg",
+      "32": "icons/icon.svg",
+      "48": "icons/icon.svg",
+      "96": "icons/icon.svg",
+      "128": "icons/icon.svg"
+    }
+  },
+  "icons": {
+    "16": "icons/icon.svg",
+    "32": "icons/icon.svg",
+    "48": "icons/icon.svg",
+    "96": "icons/icon.svg",
+    "128": "icons/icon.svg"
+  }
+}