Add Claude Code support, credential routing polish, and CYA-WP-0006

Mirror sibling-repo Claude setup (CLAUDE.md + .claude/rules/*), align
AGENTS.md with fleet credential-routing template, and close housekeeping
gaps (WP-0002-T05 done, WP-0005 status note). Draft CYA-WP-0006 for
Profile 1 production hardening as the proposed next slice.

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

@@ -0,0 +1,38 @@
+## Stack
+
+- **Language:** Python 3.11+
+- **CLI:** Typer + Rich
+- **Config:** TOML
+- **Packaging:** setuptools + setuptools_scm (`src/` layout)
+- **Tests:** pytest
+
+## Dev Commands
+
+```bash
+# Recommended: install latest development code
+make dev-install
+
+# Run tests
+make test
+# or: python3 -m pytest tests/ -q
+
+# Build distribution packages
+make dist
+make release-prep
+make check-dist
+
+# Run the assistant
+cya "your natural language request here"
+cya --help
+cya --explain-context "show me what context would be collected"
+cya retrospect
+
+# Version / inspection
+make version
+git status --short
+rg --files
+```
+
+Current memory baseline: **Profile 0** (local JSON + activation + retrospection).
+Profile 1 verbal reflections shipped as a minimal spike (CYA-WP-0005); production
+hardening tracked in CYA-WP-0006.