Port upstream 0.55.0: Cursor Grok Bot usage

[Finesssee]

Summary

• port upstream CodexBar v0.55.0 Cursor Grok Bot weekly included usage from Add Grok Bot Support to Cursor Card steipete/CodexBar#3127
• fetch /api/dashboard/get-sand-usage-status best-effort with a 5-second timeout
• surface Grok Bot as an extra Cursor usage lane only when the account has a non-zero included allowance
• keep main Cursor usage/auth success independent from the optional Sand endpoint

Upstream evidence

• target release: v0.55.0
• upstream commit: c87c35bec / Add Grok Bot Support to Cursor Card steipete/CodexBar#3127

Validation

• C:/Users/mac/.cargo/bin/cargo.exe test -p codexbar cursor -> 24 passed
• focused rustfmt on the touched Cursor files
• git diff --check -> pass

Scope

Isolated Cursor provider enhancement. No separate Grok provider state, version bump, or unrelated UI changes.

[Finesssee]

Thermo-nuclear re-review

Previous finding is closed: the positional six/seven-element Cursor tuples were replaced by a named CursorUsageResult boundary. 11/11 focused API tests and strict Clippy pass.

Verdict: APPROVED.