docs: fix flake URL and add nix run MCP example

- Update flake URL from github:torjus/labmcp to the correct
  git+https://git.t-juice.club/torjus/labmcp
- Add alternative MCP client configuration using nix run with
  the flake URL directly (no installation required)
- Fix NixOS module example to use correct flake URL

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -20,10 +20,10 @@ Search and query NixOS configuration options across multiple nixpkgs revisions.
 
 ```bash
 # Build the package
-nix build github:torjus/labmcp
+nix build git+https://git.t-juice.club/torjus/labmcp
 
 # Or run directly
-nix run github:torjus/labmcp -- --help
+nix run git+https://git.t-juice.club/torjus/labmcp -- --help
 ```
 
 ### From Source
@@ -52,6 +52,22 @@ Configure in your MCP client (e.g., Claude Desktop):
 }
 ```
 
+Alternatively, if you have Nix installed, you can use the flake directly without installing the package:
+
+```json
+{
+  "mcpServers": {
+    "nixos-options": {
+      "command": "nix",
+      "args": ["run", "git+https://git.t-juice.club/torjus/labmcp", "--", "serve"],
+      "env": {
+        "NIXOS_OPTIONS_DATABASE": "sqlite:///path/to/nixos-options.db"
+      }
+    }
+  }
+}
+```
+
 Then start the server:
 
 ```bash
@@ -178,7 +194,7 @@ A NixOS module is provided for running the MCP server as a systemd service.
 
 ```nix
 {
-  inputs.labmcp.url = "github:torjus/labmcp";
+  inputs.labmcp.url = "git+https://git.t-juice.club/torjus/labmcp";
 
   outputs = { self, nixpkgs, labmcp }: {
     nixosConfigurations.myhost = nixpkgs.lib.nixosSystem {