Fixes#1226
The Antigravity OAuth flow sent inconsistent client metadata between
the token acquisition phase and the API usage phase. String enum values
(IDE_UNSPECIFIED, PLATFORM_UNSPECIFIED) were used during OAuth token
exchange + loadCodeAssist + onboardUser, while numeric enums (ideType: 9,
platform: <computed>, pluginType: 2) were used in runtime API calls.
Google detected this fingerprint mismatch and blocked 9router accounts.
Replace all string enum occurrences with the correct numeric values:
- src/lib/oauth/constants/oauth.js: loadCodeAssistClientMetadata now
uses getOAuthPlatformEnum() for platform and numeric 9/2 for
ideType/pluginType, matching getOAuthClientMetadata()
- src/lib/oauth/services/antigravity.js: getMetadata() now delegates
to getOAuthClientMetadata() instead of returning hardcoded strings
- src/lib/oauth/providers.js: postExchange metadata now uses
getOAuthClientMetadata() instead of inline string enums
- open-sse/services/usage.js: getGeminiSubscriptionInfo body now uses
CLIENT_METADATA (already imported from appConstants.js) instead of
inline string enums
