Reading Library V4.8.2 — Studio installer folder-picker and missing-file repair

This patch addresses the browser error: "A requested file or directory could not be found at the time an operation was processed."

- New folder-picker ID to avoid the stale V4.8.1 directory bookmark.
- Picker opens at last remembered folder (where available), otherwise Downloads.
- Automatic selection of "Reading Library Files" if user chooses its immediate parent.
- A write-access preflight before decompression, with actionable error diagnostics that identify failed files.
- Teacher Mode launch file verified after extraction.
- No changes to catalogue IDs, reading assessments, existing imported resources or curricula.
- Existing users can install the UPGRADE ONLY archive over their Reading Library folder.
- Chrome/Edge first-use folder selection and permission prompt remain mandatory; HTML cannot silently select folders.

Known limit: Actual native OS folder picker requires verification on target desktops.
