feat: implement manifest entry metadata inheritance

[HeartLinked]

Summary

Implements the metadata inheritance system for manifest entries, enabling proper inheritance of
snapshot_id, sequence_number, and file_sequence_number from manifest list to manifest entries.

Changes

• Add InheritableMetadata interface with BaseInheritableMetadata, EmptyInheritableMetadata, and
  CopyInheritableMetadata implementations
• Add InheritableMetadataFactory for creating appropriate metadata inheritance instances
• Integrate metadata inheritance into ManifestReaderImpl::Entries() method

Test Plan

• Existing manifest reader tests pass with inherited metadata
• Inheritance logic properly handles snapshot_id, sequence_number, and file_sequence_number fields

This is to be completed in #178 .