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)

flake.nix

@@ -0,0 +1,68 @@
+{
+  description = "Opencode Agent Skills — development environment & runtime";
+
+  inputs = { nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable"; };
+
+  outputs = { self, nixpkgs }:
+    let
+      supportedSystems = [ "x86_64-linux" "aarch64-linux" "aarch64-darwin" ];
+      forAllSystems = nixpkgs.lib.genAttrs supportedSystems;
+    in {
+      # Composable runtime for project flakes and home-manager.
+      # Usage:
+      #   home.packages = [ inputs.agents.packages.${system}.skills-runtime ];
+      #   devShells.default = pkgs.mkShell {
+      #     packages = [ inputs.agents.packages.${system}.skills-runtime ];
+      #   };
+      packages = forAllSystems (system:
+        let
+          pkgs = nixpkgs.legacyPackages.${system};
+
+          pythonEnv = pkgs.python3.withPackages (ps:
+            with ps; [
+              # skill-creator: quick_validate.py
+              pyyaml
+
+              # xlsx: recalc.py
+              openpyxl
+
+              # prompt-engineering-patterns: optimize-prompt.py
+              numpy
+
+              # pdf: multiple scripts
+              pypdf
+              pillow # PIL
+              pdf2image
+
+              # excalidraw: render_excalidraw.py
+              playwright
+            ]);
+        in {
+          skills-runtime = pkgs.buildEnv {
+            name = "opencode-skills-runtime";
+            paths = [
+              pythonEnv
+              pkgs.poppler-utils # pdf: pdftoppm/pdfinfo
+              pkgs.jq            # shell scripts
+              pkgs.playwright-driver.browsers  # excalidraw: chromium for rendering
+            ];
+          };
+        });
+
+      # Dev shell for working on this repo (wraps skills-runtime).
+      devShells = forAllSystems (system:
+        let
+          pkgs = nixpkgs.legacyPackages.${system};
+        in {
+          default = pkgs.mkShell {
+            packages = [ self.packages.${system}.skills-runtime ];
+
+            env.PLAYWRIGHT_BROWSERS_PATH = "${pkgs.playwright-driver.browsers}";
+
+            shellHook = ''
+              echo "🔧 AGENTS dev shell active — Python $(python3 --version 2>&1 | cut -d' ' -f2), $(jq --version)"
+            '';
+          };
+        });
+    };
+}