Define VEntry and virtual filesystem (VFS) core types #398
Description
Background:
- Pipeline design requires VEntry and VFS abstractions to represent inputs/outputs.
Scope:
- Implement VEntry interface and core entry types (file, folder, document, node, archive) with metadata.
- Implement VFS mounts with precedence and RO/RW zones.
Acceptance criteria:
- VEntry and VFS types are defined with basic traversal and metadata support.
- Mount precedence and RO/RW enforcement are test-covered.