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)

.sisyphus/boulder.json

@@ -1,9 +0,0 @@
-{
-  "active_plan": "/home/m3tam3re/p/AI/AGENTS/.sisyphus/plans/rules-system.md",
-  "started_at": "2026-02-17T17:50:08.922Z",
-  "session_ids": [
-    "ses_393691db2ffe4YZvieMFehJe54"
-  ],
-  "plan_name": "rules-system",
-  "agent": "atlas"
-}