chore: harness audit fixes — prune ECC, add coverage threshold, secure settings

- Add pytest-cov with --cov-fail-under=55 (58% actual, trainers need GPU)
- Add .claude/settings.json to .gitignore (contains MCP placeholder secrets)
- Add .coverage to .gitignore

Local-only (not committed):
- Pruned agents 28->13, commands 60->21, rules 12 dirs->2 (common+python)
- Added Python post-edit hook (ruff check --fix + ruff format on .py edits)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitignore

@@ -48,4 +48,5 @@ report.xml
 .claude/hooks/
 .claude/mcp-configs/
 .claude/rules/
-.claude/skills/
+.claude/skills/
+.claude/settings.json.coverage

pyproject.toml

@@ -72,4 +72,4 @@ select = ["E", "F", "I", "N", "W"]
 [tool.pytest.ini_options]
 testpaths = ["tests"]
 markers = ["smoke: slow smoke tests that download models and run training (run with: pytest -m smoke)"]
-addopts = "-m 'not smoke'"
+addopts = "-m 'not smoke' --cov=soup_cli --cov-fail-under=55 --cov-report=term-missing:skip-covered"