fix: normalize subagent current-state visibility

[ozand]

Closes #471

Summary

Normalizes /api/subagents so the current/canonical eeepc state is readable without inferring it from nested fields.

Changes

• Adds top-level /api/subagents aliases from summary:
  • state, status
  • total_requests, result_count
  • queued_request_count, stale_request_count
  • blocked_result_count, stale_result_count, fresh_result_count
• Adds per-request current-state fields:
  • raw_request_status preserves the original request file state such as queued.
  • effective_status exposes the resolved current state after materialized result linking, e.g. completed or blocked.
  • status remains resolved/current for compatibility.
• Refines source-skew classification:
  • if canonical eeepc is selected and local state also exists, report source_skew.state=dual_roots_available, severity=informational, authoritative_source=eeepc.
  • reserve skewed for non-authoritative dual-root/conflict situations.

TDD evidence

RED before fix:

FAILED test_app_api_subagents_prefers_materialized_blocked_result_over_stale_queued_request
KeyError: 'state'

FAILED test_subagent_visibility_prefers_canonical_eeepc_state_over_stale_local
assert 'skewed' == 'dual_roots_available'

FAILED test_subagent_visibility_uses_remote_canonical_state_when_not_local
assert 'skewed' == 'dual_roots_available'

Focused GREEN:

PYTHONPATH=ops/dashboard/src:ops/dashboard python3 -m pytest \
  ops/dashboard/tests/test_app.py::test_app_api_subagents_prefers_materialized_blocked_result_over_stale_queued_request \
  ops/dashboard/tests/test_dashboard_truth_audit_gaps.py::test_subagent_visibility_prefers_canonical_eeepc_state_over_stale_local \
  ops/dashboard/tests/test_dashboard_truth_audit_gaps.py::test_subagent_visibility_uses_remote_canonical_state_when_not_local -q
3 passed in 1.75s

PYTHONPATH=ops/dashboard/src:ops/dashboard python3 -m pytest \
  ops/dashboard/tests/test_app.py::test_app_subagents_summary_marks_blocked_dominant_results_as_degraded \
  ops/dashboard/tests/test_autonomy_stagnation_dashboard.py::test_api_subagents_returns_json_with_stale_queued_request \
  ops/dashboard/tests/test_autonomy_stagnation_dashboard.py::test_api_subagents_materializes_terminal_telemetry_for_queued_request -q
3 passed in 5.79s

Full local suites:

PYTHONPATH=ops/dashboard/src:ops/dashboard python3 -m pytest ops/dashboard/tests -q
169 passed in 194.51s

python3 -m pytest tests -q
699 passed, 5 skipped in 21.29s