[KS][KEY] Flows: focus traversal & navigation keys #82

Part of #15 · Umbrella #9 · Task key KEY.focus

Goal

Verify with YAML flows: focus traversal & navigation keys.

Scope

Every line becomes ≥1 check ID in the registry and is covered by ≥1 YAML flow.

• Tab/Shift+Tab order; macOS Full Keyboard Access; Windows focus rectangles
• Escape cancels, Enter = default button, Cmd+. cancels
• Arrow navigation in lists; type-select

Deliverables

• Flows in e2e/flows/keyboard/ (format: see INFRA schema task)
• Check IDs KEY-… registered in e2e/checks/keyboard.yaml (only edit your area's file)
• Kitchen Sink screen(s) under examples/kitchen-sink/screens/keyboard/ exercising every scope item, testIDs keyboard-<screen>-<element>

Acceptance

• Platforms: macOS + Windows
• All flows pass on the release build (signed, installed), matrix light/dark × en-US/ar (+ reduceMotion where motion is involved)
• 10/10 consecutive local passes; zero retries
• Unsupported platform → flow asserts typed SparkError + truthful get*Availability()
• manualSteps only where automation is impossible, each with evidence
• Windows half runs once [KS][INFRA] Windows black-box backend (UI Automation + SendInput) and OS-state commands #51 lands; keep this issue open until both platforms pass or Windows is explicitly typed-unsupported

Blocked by

• [KS][INFRA] macOS black-box backend (AX API + CGEvent) and OS-state commands #50 — macOS black-box backend (AX API + CGEvent) and OS-state commands
• [KS][INFRA] Kitchen Sink app shell: catalog, deep links, testID convention, merge legend-apps screens #56 — Kitchen Sink app shell: catalog, deep links, testID convention, merge legend-apps screens

Agent rules

• Claim: assign yourself before starting; one PR per task with Closes #<this>; branch seth/ks-<issue>-<slug>
• Touch only your area's flows/checks/screens/goldens; shared tooling changes go through INFRA tasks
• Missing Spark API? Do not stub or add fallbacks. Open a kind:api task under the same epic, mark it as blocking this one, and stop