fix(filesystem): allow recursive directory creation

[CryoThrust]

Summary

• resolve the nearest existing ancestor when validating a new path
• preserve realpath checks for symlink escapes while allowing nested paths
• make the existing recursive create_directory contract work for arbitrarily deep paths
• update validation coverage for missing intermediate directories

Closes #4629

Validation

• git diff --check
• TypeScript/Vitest execution is currently blocked on this host because the Homebrew Node 22 binary cannot load libsimdjson.29.dylib.

[CryoThrust]

Closing this PR because #4654 already covers the same recursive create_directory path-validation fix. Avoiding duplicate implementation.