Add Grok Build agent config adapted from Claude Code setup

Wire shared AGENTS.md and Claude settings through home-manager, plus a
native Grok config (always-approve, rose-pine) and a `gb` yolo alias.

home.nix

@@ -34,8 +34,10 @@ in
       push = "git push";
       pull = "git pull";
       m = "git switch main";
+      # High-agency agent launchers (same idea across tools)
       cc = "claude --dangerously-skip-permissions";
       co = "codex --full-auto";
+      gb = "grok --yolo";
     };
   };
 
@@ -52,11 +54,29 @@ in
     };
   };
 
-  # Edit-in-place: the real file stays in my repo, ~/.config just points at it.
+  # Edit-in-place: the real file stays in my repo, the live path just points at it.
   home.file.".config/wezterm".source =
     config.lib.file.mkOutOfStoreSymlink "${dotfiles}/home/.config/wezterm";
   home.file.".config/nvim".source =
     config.lib.file.mkOutOfStoreSymlink "${dotfiles}/home/.config/nvim";
-  home.file.".config/herdr".source = 
+  home.file.".config/herdr".source =
     config.lib.file.mkOutOfStoreSymlink "${dotfiles}/home/.config/herdr";
+
+  # Claude Code settings (also read by Grok for permissions/compat)
+  home.file.".claude/settings.json".source =
+    config.lib.file.mkOutOfStoreSymlink "${dotfiles}/home/.claude/settings.json";
+
+  # Shared agent policy - one file, many harnesses
+  home.file.".claude/CLAUDE.md".source =
+    config.lib.file.mkOutOfStoreSymlink "${dotfiles}/home/AGENTS.md";
+  home.file.".codex/AGENTS.md".source =
+    config.lib.file.mkOutOfStoreSymlink "${dotfiles}/home/AGENTS.md";
+  home.file.".config/opencode/AGENTS.md".source =
+    config.lib.file.mkOutOfStoreSymlink "${dotfiles}/home/AGENTS.md";
+  home.file.".grok/AGENTS.md".source =
+    config.lib.file.mkOutOfStoreSymlink "${dotfiles}/home/AGENTS.md";
+
+  # Grok Build native config
+  home.file.".grok/config.toml".source =
+    config.lib.file.mkOutOfStoreSymlink "${dotfiles}/home/.grok/config.toml";
 }