opencode: add module

Seamlessly integrate the opencode AI assistant with Neovim — convenient
and editor-aware research, reviews, and requests.

plugins/by-name/opencode/default.nix

@@ -0,0 +1,36 @@
+{ lib, ... }:
+lib.nixvim.plugins.mkNeovimPlugin {
+  name = "opencode";
+  packPathName = "opencode.nvim";
+  package = "opencode-nvim";
+
+  maintainers = [ lib.maintainers.khaneliman ];
+
+  description = ''
+    OpenCode.nvim provides seamless integration with Claude Code for AI-assisted development.
+
+    > [!NOTE]
+    > Recommended: `snacks.enable` with `settings.input.enabled = true` for better prompt input
+    > Required: `snacks.enable` to use opencode.nvim's embedded terminal
+
+    > [!TIP]
+    > Set `opts.autoread = true` if using the `auto_reload` option.
+  '';
+
+  callSetup = false;
+  hasLuaConfig = false;
+  extraConfig = cfg: {
+    globals.opencode_opts = cfg.settings;
+  };
+
+  settingsExample = {
+    port = 8080;
+    auto_reload = false;
+    prompts = {
+      example = {
+        description = "An example prompt configuration";
+        prompt = "Write a function that returns the factorial of a number";
+      };
+    };
+  };
+}