Surface salvaged completed workers

[fazpu]

Summary

• classify workers with exit_code=0 as succeeded even if cleanup marked status=killed
• add a clear summary for workers that completed successfully but were marked killed during coordinator cleanup
• include salvaged_workers metadata in coordinator failure detail when completed workers have stdout artifacts
• keep actual failed/killed workers as the primary failure detail when present
• include worker_sessions_path for coordinator failures with worker records even when no worker actually failed

Verification

• uv run ruff format src/team_harness/tracking/worker_sessions.py src/tests/test_worker_sessions.py
• uv run ruff check src/team_harness/tracking/worker_sessions.py src/tests/test_worker_sessions.py src/tests/test_harness.py
• uv run pytest src/tests/test_worker_sessions.py src/tests/test_harness.py
• uv run pyright

Note

• Full uv run pytest still fails in two unrelated Rich console rendering assertions: src/tests/test_console.py::test_stream_token_bold_rendering and src/tests/test_console.py::test_stream_token_heading_rendering. The changed test areas pass.