fix: add timeout to prompt step subprocess execution

The prompt step subprocess.run() had no timeout, allowing a hung
LLM invocation to block the entire workflow engine indefinitely.
The shell step already defaults to 300s timeout.

Add timeout parameter (defaulting to 300s, matching shell step)
and handle subprocess.TimeoutExpired gracefully.

Author: Quratulain-bilal

src/specify_cli/workflows/steps/prompt/__init__.py

@@ -172,12 +172,14 @@ def _try_dispatch(
         project_root = (
             Path(context.project_root) if context.project_root else Path.cwd()
         )
+        timeout = config.get("timeout", 300)
 
         try:
             result = subprocess.run(
                 exec_args,
                 text=True,
                 cwd=str(project_root),
+                timeout=timeout,
             )
             return {
                 "exit_code": result.returncode,
@@ -190,6 +192,12 @@ def _try_dispatch(
                 "stdout": "",
                 "stderr": "Interrupted by user",
             }
+        except subprocess.TimeoutExpired:
+            return {
+                "exit_code": -1,
+                "stdout": "",
+                "stderr": f"Prompt timed out after {timeout} seconds.",
+            }
         except OSError:
             return None