Fix OpenClaw gateway launch: binary renamed openclaw, add gateway subcommand

The nix-openclaw package renamed the binary from openclaw-gateway to
openclaw, and the gateway now runs as a subcommand. Also adds CLAUDE.md
and openclaw-todo.md.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

nixos/home/danny/home.nix

@@ -189,6 +189,7 @@
     wget          # downloader
     # azure-cli   # TODO: remove this Azure cli tool
     gh            # github cli tool
+    claude-code   # Anthropic agentic coding CLI
     forgejo-cli   # forgejo/codeberg cli (provides fj)
     git           # version control
     jujutsu       # Git alternative

nixos/home/danny/openclaw.nix

@@ -66,7 +66,8 @@ in
     config = {
       ProgramArguments = [
         (config.home.homeDirectory + "/.local/bin/openclaw-gateway-wrapper")
-        "${pkgs.openclaw}/bin/openclaw-gateway"
+        "${pkgs.openclaw}/bin/openclaw"
+        "gateway"
       ];
       RunAtLoad = true;
       KeepAlive = true;