fix(glob): report "not found" for missing search paths

[9d2z12gwzutihg]

Summary

• Align glob path validation with grep: missing paths return Error: … not found instead of the misleading is not a directory.
• Add regression tests for nonexistent and file paths.

Problem

When the model passes a bad directory to glob, the current message suggests a type mismatch rather than a missing path. grep already distinguishes these cases.

Test plan

• Added test_glob_nonexistent_path and test_glob_path_is_file
• pytest tests/test_tools.py -q