Fix CreateByRelativePathCoreAsync file-tail detection for StorableType.Folder

[Arlodotexe]

Summary

Fixes CreateByRelativePathCoreAsync file-tail detection for StorableType.Folder to prevent treating file paths like path/to/file.txt as folder paths during folder creation.

Root Cause

The folder creation loop in CreateByRelativePathCoreAsync iterated over ALL path segments without checking if the last segment represented a file (indicated by dots suggesting extensions). This caused paths like assets/images/hero.png to create a folder named hero.png.

Fix

Added file-tail detection using existing LooksLikeFileTail helper:

• Checks if last segment looks like a file (has dots, no trailing slash)
• Reduces effective loop length to exclude file-like tail from folder creation
• Preserves existing behavior for paths with trailing slashes or no file-like segments

Validation

• ✅ Blog Generator Materialization: Fix validated during PostPageFolder refactor (Nov 9, 2025)
• ✅ Runtime Behavior: Template asset copying now succeeds (previously stalled creating hero.png folder)
• ✅ Root Cause Confirmed: Log analysis showed malformed paths like /C:\/Users/.../images/hero.png before fix