feat: clarify isolated Hermes doctor repairs

[cafitac]

Summary

• make hermit doctor --fix --hermes-home ... echo the targeted Hermes config directory
• cover the new output in doctor CLI/dispatch tests
• document the isolated repair-summary behavior in Hermes docs and roadmap/changelog

Test Plan

• .venv/bin/python -m pytest tests/test_cli_defaults.py::test_main_dispatches_doctor_fix tests/test_doctor_cli.py::test_format_doctor_fix_summary_includes_repair_status -q
• .venv/bin/python -m pytest tests/test_cli_defaults.py tests/test_doctor.py tests/test_doctor_cli.py tests/test_repo_hygiene.py -q
• .venv/bin/python -m pytest tests/ -q
• .venv/bin/hermit doctor --help
• .venv/bin/hermit doctor --fix --hermes-home