refactor(launcher): hardcode Gitea channel in lib/baked-gitea-channel.js

- Merge baked base_url/owner/repo/release_tag at load time (no inject script,
  no fractured-release-channel.json, no CI env for pack).
- Fix mergeConfig deep-merge for gitea, patch_manifest, launcher_updates_from_github.
- Remove inject-release-channel.js and fractured-release-channel.json.

Co-authored-by: Cursor <cursoragent@cursor.com>

tools/fractured-launcher-electron/package.json

@@ -9,8 +9,8 @@
   },
   "scripts": {
     "start": "electron .",
-    "pack:win": "node scripts/inject-release-channel.js && electron-builder --win nsis portable --x64 --publish never",
-    "publish:win": "node scripts/inject-release-channel.js && electron-builder --win nsis portable --x64 --publish never"
+    "pack:win": "electron-builder --win nsis portable --x64 --publish never",
+    "publish:win": "electron-builder --win nsis portable --x64 --publish never"
   },
   "author": "",
   "license": "GPL-3.0",
@@ -35,6 +35,7 @@
       "renderer.js",
       "styles.css",
       "default-launcher.json",
+      "lib/baked-gitea-channel.js",
       "lib/gitea-release.js",
       "lib/patch-manifest.js",
       "lib/**/*"