feat(dev-orchestrator): add NixOS home-manager module

- New module: modules/home-manager/dev-orchestrator/
- Wraps script via writeShellApplication, git as runtime dep
- opencode + openspec already in PATH via existing modules
- Enabled in jpporta-nixos home.nix

After rebuild: dev-orchestrator available in PATH

modules/home-manager/dev-orchestrator/default.nix

@@ -0,0 +1,16 @@
+{ lib, config, pkgs, ... }:
+{
+  options.custom = {
+    dev-orchestrator.enable = lib.mkEnableOption "enable dev-orchestrator — OpenSpec + OpenCode dev→QA loop with git worktrees";
+  };
+
+  config = lib.mkIf config.custom.dev-orchestrator.enable {
+    home.packages = [
+      (pkgs.writeShellApplication {
+        name = "dev-orchestrator";
+        runtimeInputs = with pkgs; [ git ];
+        text = builtins.readFile ../../../tooling/dev-orchestrator;
+      })
+    ];
+  };
+}