docs: update AGENTS.md and README.md for rules system, remove beads

- Add rules/ directory documentation to both files
- Update skill count from 25 to 15 modules
- Remove beads references (issue tracking removed)
- Update skills list with current active skills
- Document flake.nix as proper Nix flake (not flake=false)
- Add rules system integration section
- Clean up sisyphus planning artifacts
- Remove deprecated skills (memory, msteams, outlook)

.gitignore

@@ -8,3 +8,7 @@
 .sidecar-start.sh
 .sidecar-base
 .td-root
+
+# Nix / direnv
+.direnv/
+result