Downgrade pydantic check to warning; agent installs it if missing

Author: Monkatraz

codegen-llm/src/codegen.ts

@@ -160,17 +160,19 @@ function validatePrerequisites(opts: CodegenOptions): void {
     );
   }
 
-  // Check Python + pydantic are available
+  // Check Python + pydantic are available.  Not fatal — the Codex agent has
+  // full access and can install pydantic itself during the run.
   try {
     const version = execSync(
       'python3 -c "import pydantic; print(pydantic.VERSION)"',
       { encoding: "utf8", stdio: ["pipe", "pipe", "pipe"] },
     ).trim();
     log(opts, `Found pydantic ${version}`);
   } catch {
-    throw new Error(
-      "Python 3 with pydantic >= 2.9.0 is required.\n" +
-        "Install with:  pip install 'pydantic>=2.9.0'",
+    console.warn(
+      "Warning: pydantic not found on the host Python.\n" +
+        "The Codex agent will attempt to install it, but you can also run:\n" +
+        "  pip install 'pydantic>=2.9.0'",
     );
   }
 }

codegen-llm/src/prompts.ts

@@ -194,6 +194,9 @@ This script:
 
 ## Process
 
+0. First, make sure pydantic is installed:
+   \`pip install 'pydantic>=2.9.0'\`
+   (Skip if it's already available.)
 1. Start by reading the service registry in the TypeScript source to get the
    full list of services.
 2. Read the TypeScript source for a few representative services to understand