[nrodd]

Stacked on #54 (static snippet install). Review that first; this PR's diff is only the mobile changes.

What

Mobile projects are now detected and get Fullstory's native mobile SDK installed by the coding agent, instead of the web snippet.

• Detection (src/platform.ts): Flutter from pubspec.yaml (only when it depends on the Flutter SDK), Expo or bare React Native from package.json. Mobile skips the snippet fetch and the static installer.
• Org config: the org id from login (format-checked before it goes in the prompt) and, for EU orgs only, the server URL are filled into the Expo plugin org/host, Gradle fullstory { org, serverUrl }, and the plist Fullstory dict (OrgId, ServerUrl).
• New templates built from the Fullstory RN, Flutter, Android, and iOS getting-started guides:
  • React Native: Expo-managed and bare paths, Babel plugin, Podfile and asset-uploader build phase, a heads-up about the RN 0.74 to 0.78 patch, and an Expo Go caveat.
  • Flutter: runFullstoryApp/FullstoryBinding, the required Android Application subclass, version pairing between the Flutter package and the Android plugin, and notes on obfuscated builds.
  • Extras for both: FullStory.identify/FS.identify, the session URL for analytics linkage, and fsClass vs. FSMask/FSExclude for masking.
• Reference section: mobile prompts point at Fullstory's mobile docs instead of the web llms.txt.
• Analytics detection: adds RN packages and Flutter pubspec.yaml packages.
• Copy: the demo guide and outro say rebuild/ship a build instead of restart the dev server/deploy.
• Fix: removes the old React Native line in the web template that told agents to call init({ orgId }).

Decisions worth a look

• enabledVariants 'all' in Gradle so a debug build captures right away (Fullstory's default is release only). The agent tells the user they may want to narrow it later.
• The agent looks up the latest SDK version rather than us pinning one.
• The iOS asset-uploader build phase is added by editing project.pbxproj, or the agent hands it to the user if it can't do that safely. This is the step most worth testing on a real app.
• One org id for all build variants (no per-variant orgs map).

Testing

• npm run typecheck, npm run build, and npx vitest run pass (114 tests, including the new src/platform.test.ts covering detection, org id validation, US vs. EU prompt rendering, and analytics detection from pubspec).
• Not yet run end to end against a real RN, Expo, or Flutter app.