V1 security enhancement

[ShreyPurohit]

Added

• Webview preview with live validation
• Format Selector in Webview
• Replace/Skip/Cancel prompt when target items already exist (uses Trash for Replace)
• Support for JSON file leaves as string file types (e.g., "route": "ts")
• Safer, remote-ready filesystem via vscode.workspace.fs
• Tree symbol constants for consistent, readable Unicode output (├──, └──, │)

Changed

• Plain Text parser is now strict: requires connectors, enforces single root directory, consistent indentation, and ignores the first line as header
• Plain Text creation asks confirmation before proceeding if input is invalid
• Formatter outputs readable tree; JSON output reflects new file-leaf format
• Webview UI modernized (two-column layout, status badge, copy preview, clear input)

Fixed

• Various encoding issues in tree drawing by using Unicode consistently
• Type-safe configuration access and better error handling