Add strip_fences option and fix exec() scoping for nested functions

- Add strip_fences field to PromptStep for removing markdown code fences
- Fix exec() to use same dict for globals and locals, allowing nested
  functions to access module-level imports
- Add GUI checkbox for strip_fences option
- Update CLAUDE.md with improved documentation

Co-Authored-By: Claude Opus 4.5 <[email protected]>

src/cmdforge/runner.py

@@ -221,7 +221,13 @@ def execute_prompt_step(
         print(f"Error in prompt step: {result.error}", file=sys.stderr)
         return "", False
 
-    return result.text, True
+    text = result.text
+    if step.strip_fences:
+        import re
+        text = re.sub(r'^```\w*\n', '', text.strip())
+        text = re.sub(r'\n```\s*$', '', text)
+
+    return text, True
 
 
 def execute_code_step(
@@ -245,11 +251,15 @@ def execute_code_step(
     code = substitute_variables(step.code, variables, warn_non_scalar=verbose)
 
     # Create execution environment with variables
-    local_vars = dict(variables)
+    # IMPORTANT: Use the same dict for both globals and locals.
+    # When exec() gets separate dicts, nested functions can't access
+    # module-level imports (they look in globals, not the exec's locals).
+    local_vars = {"__builtins__": __builtins__}
+    local_vars.update(variables)
 
     try:
         # Execute the code with substituted variables
-        exec(code, {"__builtins__": __builtins__}, local_vars)
+        exec(code, local_vars, local_vars)
 
         # Support comma-separated output vars (e.g., "a, b, c")
         output_vars = [v.strip() for v in step.output_var.split(',')]