chore: migrate CLAUDE.md to @-import rule structure (custodian integration)

Register with state-hub under custodian domain. Replace monolithic CLAUDE.md
with thin @-import index; distribute content into .claude/rules/ per ops-bridge pattern.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/rules/stack-and-commands.md

@@ -0,0 +1,43 @@
+## Stack and Commands
+
+**Language:** Python 3.8+
+**Package manager:** uv / pip (`.venv/`)
+**Test runner:** pytest
+**Linter/formatter:** flake8 (100-char), black (88-char), mypy (strict)
+
+### Essential commands
+
+```bash
+make setup-complete     # First-time setup: venv + package + dev deps
+source .venv/bin/activate
+make test               # Run full test suite
+make lint               # flake8 linting
+make format             # black formatting
+make clean              # Remove build artifacts
+```
+
+### TDD workflow
+
+```bash
+make tdd-start ISSUE=X  # Start issue with requirements validation
+make tdd-add-test       # Add test to current workspace
+make tdd-status         # Show workspace state
+make tdd-finish         # Move tests to main suite
+```
+
+### Issue management
+
+```bash
+make issue-list         # All issues (Gitea)
+make issue-list-open    # Open backlog
+make issue-show ISSUE=X # Issue detail
+make issue-create TITLE='...' BODY='...'
+```
+
+Run `make help` to see all available targets.
+
+### Core dependencies (pyproject.toml)
+
+- `pyyaml>=6.0` — YAML config
+- `click>=8.0.0` — CLI framework
+- `pydantic>=2.0.0` — Data validation