fix: accept digit-leading loop names in is_sam_generated_mapping

A ForEach loop named Fn::ForEach::1stBatch produces a mapping name
like SAMCodeUri1stBatch. The character after the prefix (SAMCodeUri)
is '1', which failed the uppercase-only check. This caused
_update_sam_mappings_relative_paths to skip the mapping (broken
artifact paths in build output) and _create_deploy_error to miss it
(raw CFN error instead of helpful re-package guidance).

Now accepts digits as well as uppercase letters after the prefix.
All SAM-generated prefixes end in a letter (CodeUri, ImageUri, etc.)
so a digit unambiguously indicates the start of the nesting path.

Author: bnusunny

samcli/lib/cfn_language_extensions/utils.py

@@ -87,7 +87,9 @@ def is_sam_generated_mapping(mapping_name: str) -> bool:
             return False
         if mapping_name.startswith(prefix):
             nxt = mapping_name[len(prefix)]
-            if "A" <= nxt <= "Z":
+            # Accept uppercase letter (PascalCase nesting path) or digit
+            # (loop names like "1stBatch" produce SAMCodeUri1stBatch).
+            if ("A" <= nxt <= "Z") or ("0" <= nxt <= "9"):
                 return True
     return False
 

tests/unit/commands/deploy/test_exceptions.py

@@ -177,6 +177,8 @@ def test_sam_generated_names_match(self):
             "SAMContentUriLayers",
             "SAMDefinitionUriEnvsFunctions",
             "SAMImageUriFunctionsApi",
+            # Digit-leading loop name: Fn::ForEach::1stBatch
+            "SAMCodeUri1stBatch",
         ):
             with self.subTest(name=name):
                 self.assertTrue(is_sam_generated_mapping(name))