Show API key usage mode in ReviewMonitor

[lynnswap]

Purpose

API key authentication does not expose the ChatGPT rate-limit windows used by ReviewMonitor's quota gauges. Present this as a normal provider state instead of leaving placeholder gauges visible indefinitely.

Changes

• Add a capability-driven usage presentation for loading, gauge, and provider states.
• Show Using API Key for API key accounts (and provider-specific labels for other accounts without Codex rate-limit support).
• Hide rate-limit refresh and detail controls when the account does not support them.
• Add presentation and rendered menu regression coverage.

Validation

• swift test --build-system swiftbuild --no-parallel
• xcodebuild test -project Tools/ReviewMonitor/CodexReviewMonitor.xcodeproj -scheme CodexReviewMonitor -destination 'platform=macOS,arch=arm64' CODE_SIGNING_ALLOWED=NO CODE_SIGNING_REQUIRED=NO
• Local Codex review against main: 0 findings