Match Finder table resizing behavior

[lyc280705]

What changed

• use AppKit's first-column-only autoresizing so window resizing changes only the Name column
• snap unused table width back into the Name column, matching Finder's fitted layout
• preserve horizontal scrolling when user-resized columns exceed the viewport
• keep the Name column pinned first while allowing the remaining columns to be reordered
• bump the release build and documentation to CleanZip 2.6.31

Root cause

The previous custom vertical-only scroll view forced the table width to the viewport and repeatedly resized the last column. That bypassed NSTableView's native document sizing and prevented Finder-style column behavior.

Validation

• built universal arm64 and x86_64 app and Finder service locally
• verified AppKit first-column autoresizing with a focused probe
• verified initial fitting and window growth in the running CleanZip UI
• validated both Info.plist files and checked the diff for whitespace errors