Start CompactGUI UI overhaul foundation

[marcmy]

Summary

• rename the top-level Home navigation item to Compress
• replace the Home glyph with a custom two-arrow outline modeled after CompactGUI's application icon: exactly two diagonal arrows pointing inward toward the center, not Fluent's four-arrow move-inward symbol
• rename the main manual action from Compress Selected to Compress Now
• require confirmation before Apply to all copies the currently shown compression settings to the other added folders
• let users manually scroll the live compression details list without ScrollIntoView immediately snapping them back to the current file; auto-follow resumes 5 seconds after the last manual scroll/drag
• enforce a 28px minimum vertical scrollbar thumb height for the large compression details list
• hide the Details grid's horizontal scrollbar
• keep subtle vertical column-resize boundaries visible even when the pointer is not hovering over a header
• replace the generic red X compression-stop glyph with a compact red stop-sign-style icon

Details behavior

The details list continues following the currently processed file normally. Any manual vertical scroll starts a 5-second suppression window. Dragging the thumb keeps that window alive for the duration of the drag and starts a fresh 5 seconds when released. Once the window expires, normal auto-follow resumes on the next current-file update.

The Details table is intended to fit the available width, so horizontal scrolling is disabled. Column resizing remains enabled; each header now keeps a subtle 1px right-edge separator visible at rest while preserving WPF-UI's existing resize gripper hit target.

Stack

This PR is stacked on #28, which is stacked on #24. Builds from agent/ui-overhaul-foundation therefore include the manual resume/exit fixes and corrected non-compressible-file filtering.

The charcoal/gray visual theme remains in #27 on top of this branch.

Runtime checks

1. Verify the first navigation tab reads Compress and shows exactly two diagonal outlined arrows pointing inward toward the center, proportionate to Watcher/Database icons.
2. Verify the idle action reads Compress Now through state/template changes.
3. Click Apply to all; Cancel must make no changes, while Yes must clone the currently displayed settings to eligible folders.
4. During a large manual compression, drag/wheel-scroll the Details list and verify it stays under user control for 5 seconds before auto-follow resumes.
5. Verify the Details vertical scrollbar remains practically grabbable even with tens of thousands of files and that no horizontal scrollbar appears.
6. Verify column resize boundaries remain visible without hover and are still draggable.
7. Verify the compression stop button uses the red stop-sign-style glyph and retains the existing stop behavior.