fix(ai): scoped antigravity quota blocks by model family

- Added CredentialRankingStrategy scope hooks so providers can rank and block only the limits relevant to the requested model.
- Scoped Antigravity usage reports by model family: Gemini/Gemma use Google counters, Claude uses Anthropic counters, and GPT/OpenAI models use OpenAI counters.
- Added scoped backoff keys so a Gemini quota block no longer suppresses healthy Claude/OpenAI Antigravity sessions on the same OAuth credential.
- Threaded modelId through coding-agent API-key resolvers and usage-limit rotation paths.
- Added regression coverage proving a Google/Gemini exhaustion block still allows Claude selection on the same credential.

Fixes #2198

packages/coding-agent/src/utils/commit-message-generator.ts

@@ -115,6 +115,7 @@ export async function generateCommitMessage(
 					apiKey: registry.resolver(candidate.model.provider, {
 						sessionId,
 						baseUrl: candidate.model.baseUrl,
+						modelId: candidate.model.id,
 					}),
 					maxTokens,
 					reasoning: toReasoningEffort(candidate.thinkingLevel),