Fix hypothesis routing and shell churn labels

[douglasmonsky]

Summary

• route exploratory low-output/context-pressure/repeated-read hypotheses to the correct usage families instead of falling back to broad effort or allowance signals
• reuse the shared command normalizer for content-index command roots so shell wrappers, $PWCLI, poetry run, uv run, npx, and python -m index consistently
• make shell-churn output less cloudy with quality, custom_command, and unclassified_shell families instead of overusing unknown
• add regressions for the exact misrouted hypotheses and shell-churn label cases from the local experiment

Validation

• PYTHONPATH=src .venv/bin/python -m pytest tests/reports/test_hypothesis_routing.py tests/store/test_content_index.py::test_command_root_and_label_uses_shared_safe_normalizer tests/store/test_content_index.py::test_shell_churn_display_labels_repair_legacy_unknown_command_rows tests/store/test_content_index.py::test_shell_churn_detects_repeated_command_families -q --tb=short
• .venv/bin/python -m ruff check .
• .venv/bin/python -m mypy
• PYTHONPATH=src .venv/bin/python -m pytest tests/reports/test_hypothesis_routing.py tests/store/test_content_index.py tests/cli/test_mcp_integration.py -q --tb=short
• PYTHONPATH=src .venv/bin/python -m pytest -q --tb=short
• PYTHONPATH=src .venv/bin/python -m pytest --cov=codex_usage_tracker --cov-report=term-missing -q
• .venv/bin/python -m compileall src
• for file in src/codex_usage_tracker/plugin_data/dashboard/dashboard*.js; do node --check "$file"; done
• .venv/bin/python scripts/check_release.py && git diff --check
• rm -rf dist build src/codex_usage_tracker.egg-info src/codex_usage_tracking.egg-info && .venv/bin/python -m build && .venv/bin/python -m twine check dist/* && .venv/bin/python scripts/check_release.py --dist && git diff --check
• real-data probe: families now route to token_waste, repeated_file_rediscovery, allowance_change; shell top families show unclassified_shell, quality, package, test, file_discovery instead of generic unknown_command