v-0.2.1: Remote SSH compatibility

[ShreyPurohit]

• Remote SSH/provider compatibility for copy/create structure by keeping filesystem operations Uri-native end-to-end (no early fsPath conversion).
• Plain Text multi-root parsing for service-style trees and root-level file entries.
• Plain Text validation handling for decorative separator lines between root blocks.
• Tree formatter root-level connector behavior (├── / └──) and spacing between root sections.
• JSON structure support for null file leaves (e.g. "Dockerfile": null) in validation, preview, and creation.

Issue: #9