[ltmoerdani]

Fixes #273

Summary

• Read the authoritative usage.opencode.allowance value from OpenCode responses.
• Track allowance-based usage for OpenCode Go, with the existing local estimate only as a fallback.
• Preserve server-provided percentage and reset time as authoritative account-wide meters.
• Stop deriving a misleading global $60/model-dependent limit from one hardcoded triple.
• Show server-backed local amounts without presenting an invented nominal limit.
• Keep non-Go providers and existing fallback behavior unchanged.

Verification

• npm run lint ✅
• npm run compile ✅
• npm run test-retry ✅
• git diff --check ✅
• Live request in VS Code Extension Development Host using local OpenCode Go / Kimi K3 ✅
• Usage dashboard confirmed synced server meters and dynamic local amounts.

The implementation details and limitation are documented in docs/issues/119-20261031-issue273-dynamic-go-allowance.md.