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>

README.md

@@ -116,6 +116,41 @@ nftablesbuilder.eu (served with a self-signed certificate, hence the
 `curlOpts = "-k"` in the derivation); the source repository is missing the
 `settings` crate, which this overlay patches in.
 
+### OpenCodeReview OpenCode Plugin (Home Manager)
+
+The `open-code-review` package bundles its OpenCode plugin (the plugin file
+plus runtime `node_modules`) as `passthru.opencode-plugin`, built from the
+same source revision as the CLI. A Home Manager module symlinks it into
+`~/.config/opencode/plugins/` and puts the `ocr` CLI on PATH:
+
+```nix
+inputs.millerson-nix-overlay.url = "git+https://git.millerson.name/alex/millerson-overlay.nix.git";
+inputs.home-manager.url = "github:nix-community/home-manager";
+```
+
+```nix
+# in your home-manager configuration
+imports = [ millerson-nix-overlay.homeManagerModules.default ];
+
+programs.open-code-review = {
+  enable = true;
+  opencode.enable = true; # symlink plugin into ~/.config/opencode
+};
+```
+
+Without Home Manager, symlink manually:
+
+```bash
+plugin=$(nix build --print-out-paths \
+  git+https://git.millerson.name/alex/millerson-overlay.nix.git#open-code-review.passthru.opencode-plugin)
+mkdir -p ~/.config/opencode/plugins
+ln -sf $plugin/share/open-code-review/opencode/open-code-review.ts ~/.config/opencode/plugins/
+ln -sfn $plugin/share/open-code-review/opencode/node_modules ~/.config/opencode/plugins/node_modules
+```
+
+Note: the `node_modules` symlink is shared across everything in the plugins
+directory; other manually-installed plugins with conflicting npm dependencies
+cannot coexist with it.
 
 ## Development