fix(clean): empty trash without Finder dialog and keep spinner alive

Two UX regressions in mo clean's user-essentials phase:

1. Trash empty triggered macOS's "Show warning before emptying the
   Trash" dialog because the implementation routed through Finder
   AppleScript. mo clean blocked on user confirmation until the dialog
   was answered, defeating the unattended cleanup expectation. Drop
   the Finder branch entirely and always direct-delete via
   safe_remove. Volume Trashes (/Volumes/*/.Trashes/<uid>/) were never
   advertised as supported and remain outside scope.

2. After "Darwin user temp files" printed, the cache scan and trash
   empty ran with no spinner, so the terminal looked frozen for
   seconds. Restart the section spinner between the two Darwin runtime
   passes and start an inline spinner inside clean_trash while items
   are being removed. User now sees continuous progress through the
   whole phase.

Test renamed from "falls back when Finder trash operations time out"
to "empties trash directly without Finder prompt" and stubs osascript
to assert it is never invoked.