feat: notify when quota windows reset

[ignaciodiazjimenez]

Summary

Add opt-in, provider-neutral reset notifications for quota windows.

The observer reuses already-fetched provider results, records a hashed account/window identity in local state, and emits one aggregated success toast only after the previous reset boundary is crossed, the provider advertises a newer reset, and remaining quota increases. It adds no provider requests and defaults to disabled.

{
  "resetNotifications": {
    "enabled": true,
    "windows": ["weekly"]
  }
}

Linked Issue

Fixes #199

OpenCode Validation

• Current production released OpenCode version tested: 1.18.11
• Why this version is relevant to the fix: it provides the production TUI success-toast surface used by the notification. The behavior was first validated with a local multi-account quota prototype before being generalized here.

Verification

• pnpm verify passed through the repository pre-push hook on Node 24/Linux
• Includes Biome, TypeScript 7 typecheck, build, all 1,809 tests, cross-surface tests, and package-content checks
• Added detector, persistence, configuration, account-isolation, and server-toast integration coverage

Quality Checklist

• I ran pnpm run typecheck
• I ran pnpm run build
• I ran pnpm test
• This change is focused and avoids unrelated behavior changes
• I updated or added tests when behavior changed
• I updated docs when user-facing workflow, command, or config behavior changed
• Provider Changes does not apply; no provider implementation or credential flow changed

[slkiser]

@ignaciodiazjimenez Thanks!