feat(shell): add pi-coding-agent and omp module

modules/hm/shell/pi.nix

@@ -0,0 +1,36 @@
+{
+  flake.modules.homeManager.shell = {pkgs, ...}: {
+    home.file.".pi/agent/auth.json".text = builtins.toJSON {
+      google = {
+        type = "api_key";
+        key = "!cat /run/secrets/gemini-api-key";
+      };
+      openrouter = {
+        type = "api_key";
+        key = "!cat /run/secrets/openrouter-api-key";
+      };
+      opencode-go = {
+        type = "api_key";
+        key = "!cat /run/secrets/opencode-go-api-key";
+      };
+      zai = {
+        type = "api_key";
+        key = "!cat /run/secrets/zai-coding-plan-api-key";
+      };
+    };
+
+    programs.pi-coding-agent = {
+      enable = true;
+      package = pkgs.llm-agents.pi;
+
+      settings = {
+        defaultModel = "glm-5.3-flash";
+        defaultProvider = "zai";
+        defaultThinkingLevel = "medium";
+        theme = "dark";
+      };
+    };
+
+    home.packages = with pkgs; [llm-agents.omp];
+  };
+}