feat(tray): 트레이 런타임 상태 표시 추가

[dkfhddla]

Summary

• Add an in-memory active request registry and instrument proxied request paths after routing selection.
• Expose a local-only /api/runtime/status endpoint that combines active request summaries with 5-hour usage state.
• Extend the Windows tray tooltip and menu with 5h usage, reset countdowns, account status, and active request summaries.
• Add OpenSpec deltas and targeted unit/integration coverage.

Validation

• python -m pytest tests/unit/test_active_requests.py tests/unit/test_runtime_status_api.py tests/unit/test_tray_runtime_formatting.py tests/integration/test_runtime_status_api.py tests/unit/test_tray.py tests/integration/test_usage_api.py -q with TMP/TEMP pointed at workspace .tmp
• python -m ruff check app/core/active_requests.py app/modules/runtime_status app/dependencies.py app/main.py app/modules/proxy/api.py app/modules/proxy/service.py app/tray.py tests/unit/test_active_requests.py tests/unit/test_runtime_status_api.py tests/unit/test_tray_runtime_formatting.py tests/integration/test_runtime_status_api.py
• python -m ty check app/core/active_requests.py app/modules/runtime_status app/tray.py tests/unit/test_active_requests.py tests/unit/test_runtime_status_api.py tests/unit/test_tray_runtime_formatting.py tests/integration/test_runtime_status_api.py

Notes

openspec validate --specs could not run locally because the openspec executable is not available on PATH in this environment.

[dkfhddla]

LGTM. base 브랜치 기준 지침과 OpenSpec 변경 흐름을 확인했고, active request 등록/정리 경로와 runtime status/tray 표시 흐름을 diff 및 주변 코드로 검토했습니다. 주요 신규 테스트도 로컬에서 통과해 차단 이슈는 발견하지 못했습니다. 참고로 GitHub 정책상 작성자 본인 PR에는 approve review를 남길 수 없어 COMMENT로 남깁니다.