feat(google-agy): migrate to retrieveUserQuotaSummary API

[anthonyhaussman]

Summary

Following the last release of opencode-agy-auth, switch from per-model retrieveUserQuota to grouped retrieveUserQuotaSummary endpoint.

The new API returns model families (e.g. "Gemini Models", "Claude and GPT models") with weekly/5h buckets, eliminating client-side model name parsing and aggregation.

Add rankOverride/groupSortOverride fields for explicit intra-group and inter-group ordering.
Filter disabled buckets before display.
Merge summary groups across accounts keeping minimum remainingFraction.

New display:

> node dist/bin/opencode-quota.js show --provider google-agy
[Google AGY · Gemini Models]
Weekly window                                   2d
██████████████░░░░░░░░░░░░░░░░░░░░░░░░░   35% left
5h window                                       5h
██████████████████████████████████████░   97% left

[Google AGY · Claude and GPT models]
Weekly window                                   4d
███████████████████████████████░░░░░░░░   79% left
5h window                                         
███████████████████████████████████████  100% left

Linked Issue

Improve the display of opencode-agy Google AntiGravity quota to be in accordance with the Antigravity client.

OpenCode Validation

• Current production released OpenCode version tested: 1.17.10
• Why this version is relevant to the fix: -

Quality Checklist

• I ran pnpm run typecheck
• I ran pnpm test
• I ran pnpm run build
• This is the smallest safe root-cause fix (no unnecessary hook/output mutation logic)
• I preserved behavioral invariants and updated/added boundary tests as needed
• I updated docs for user-facing workflow/command/config changes (README.md and CONTRIBUTING.md when applicable)
• For new API-key/token providers, I started from contributing/provider-template/ or explained why the template does not apply
• For provider setup/auth wording changes, I checked the relevant dummy .ts template in contributing/provider-template/ and verified README.md against src/lib/provider-metadata.ts (authentication/authFallbacks) and provider auth resolver/diagnostics behavior