feat: bundle opencode plugin as open-code-review passthru + HM module

- packages/open-code-review/opencode-plugin.nix: builds the plugin TS file
  plus runtime node_modules from the plugin's package-lock.json into
  share/open-code-review/opencode (exposed as passthru.opencode-plugin,
  same source rev as the CLI so versions stay locked)
- modules/open-code-review-hm.nix: homeManagerModules.default with
  programs.open-code-review.{enable,opencode.enable} — symlinks the plugin
  and node_modules into ~/.config/opencode/plugins/ and installs the CLI
- flake.nix: expose homeManagerModules.default

Note: upstream declares the plugin SDKs as devDependencies, so the
lockfile install must not use --omit=dev.

🤖 Generated with Codebuff
Co-Authored-By: Codebuff <noreply@codebuff.com>

packages/open-code-review/package.nix

@@ -2,6 +2,7 @@
   lib,
   buildGoModule,
   fetchFromGitHub,
+  callPackage,
 }:
 
 buildGoModule rec {
@@ -33,6 +34,10 @@ buildGoModule rec {
 
   passthru = {
     category = "Code Review";
+    # OpenCode plugin built from the same source revision as the CLI.
+    opencode-plugin = callPackage ./opencode-plugin.nix {
+      inherit src version;
+    };
     updateScript = [
       "nix-update"
       "--flake"