Add Unity Windows release tooling

[SilverSupplier]

Summary

• Add a Unity Editor menu and batchmode entry point for building the Magic Exam Hall Windows player.
• Register the Magic Exam Hall scene before building and fail batchmode builds when BuildPipeline reports a non-success result.
• Add a Windows player smoke script that launches the generated build headlessly, waits for startup markers, and fails on early exit or fatal startup log patterns.
• Add a release candidate checklist covering Web verification, Unity tests, Windows build smoke, manual five-floor playthrough, logs/privacy, and submission packaging.

Related Issues

• Closes: [Child #18] Windows Unity batchmode build method 추가 #51, [Child #18] 릴리스 후보 체크리스트 문서화 #52
• Related: [Release] Unity 실행 빌드와 제출 체크리스트 준비 #18, [Child #18] 생성된 Windows 빌드 smoke test #53
• Follow-up: [Child #18] 생성된 Windows 빌드 smoke test #53 still needs visible manual QA for WASD movement and right-mouse drawing.

Merge Order

• Independent from the active gameplay PRs (Feat: tune Magic Exam Hall world casting timing #58, Strengthen final floor guidance and ending #63, Differentiate floor 3 and 4 world reactions #65); this only touches release tooling, generated-output hygiene, release docs, and the Unity README.
• Can merge once checks pass. If another docs PR lands first, re-check README/checklist conflicts.

Verification

• npm run validate:docs; Not run directly because local node.exe was blocked by permissions.
• node scripts/validate-doc-state.mjs via bundled Codex Node: passed after the checklist update.
• npm test; Not run, release tooling/docs only.
• npm run build; Not run, release tooling/docs only.
• Unity EditMode tests: 19 passed before the smoke/checklist follow-ups.
• Unity PlayMode tests: Not run, no gameplay/runtime behavior changed.
• Unity Windows batchmode build via MagicExamHall.Editor.MagicExamHallBuildPipeline.BuildWindowsPlayer: succeeded with 0 errors and 0 warnings.
• powershell -NoProfile -ExecutionPolicy Bypass -File .\scripts\smoke-magic-exam-hall-player.ps1 -BuildPath 'unity/MagicExamHall/Builds/MagicExamHall.exe' -LogPath 'unity/MagicExamHall/player-smoke-pr69.log' -TimeoutSeconds 8: passed.
• GitHub checks observed after latest push: validate-docs, build, test, and CodeQL passed.

Notes

• Scope: Windows player build entry point, output-path argument parsing, scene registration for player builds, generated-player startup smoke coverage, release checklist, generated Unity test-result ignore patterns, and README release commands.
• Out of scope / follow-up: visible manual QA for player movement plus right-mouse world drawing ([Child #18] 생성된 Windows 빌드 smoke test #53).
• Risk notes: requires Windows Standalone build support in the installed Unity editor. The smoke script checks startup and scene-load log markers, but it does not replace visible human playtesting.

Review Checklist

• This PR changes user-facing UI or behavior.
• This PR changes recognizer behavior.
• This PR changes docs, task state, or project process.
• This PR changes ML artifacts, datasets, generated outputs, or capture/export behavior.
• This PR changes logging, survey fields, privacy, or research data handling.
• This PR needs screenshots or a short playtest note.

Screenshots / Playtest Notes

Generated Windows player smoke passed headlessly: the player stayed alive for 8 seconds, wrote startup log markers, and did not log fatal startup patterns. The new release checklist keeps visible five-floor playthrough and logs/privacy review as required manual checks before submission.