prune,ui: show the removal pass, prefix the sizing spinner

Confirming a 500 GiB prune went silent under "Removing:" for minutes:
drive an indicatif bar from the plan's sizes through a new
apply_with_progress observer, in the deb live view's layout — the
running count behind the spinner on the first line, the byte bar with
its counters on the second. The removed path is not rendered: it
fights the bar on a narrow terminal, and the failed-removal errors
name the paths that matter. --force plans no sizes and gets the count
line only.

The dry-run size spinner lacked the "> " prompt prefix the other
one-line waits carry; wait_spinner renders it too now.

src/ui/deb.rs

@@ -488,7 +488,7 @@ fn drop_pane(shared: &Shared) {
 /// Render the pane content with per-kind colors, ellipsizing lines that are
 /// wider than the terminal so they do not overflow onto a wrapped line
 fn render_pane(lines: &VecDeque<(Kind, String)>) -> String {
-    let max_width = terminal_width().map(|w| w.saturating_sub(PANE_PREFIX_WIDTH));
+    let max_width = crate::ui::terminal_width().map(|w| w.saturating_sub(PANE_PREFIX_WIDTH));
     render_pane_with_width(lines, max_width)
 }
 
@@ -515,13 +515,6 @@ fn render_pane_with_width(lines: &VecDeque<(Kind, String)>, max_width: Option<us
 /// Display width of the `  │ ` prefix rendered before each pane line
 const PANE_PREFIX_WIDTH: usize = 4;
 
-/// Width of the terminal in columns, or `None` when it cannot be determined
-fn terminal_width() -> Option<usize> {
-    crossterm::terminal::size()
-        .ok()
-        .map(|(cols, _)| cols as usize)
-}
-
 /// Ellipsize `text` to at most `max_width` display columns, keeping its head
 /// and appending `…` when it does not fit
 fn ellipsize(text: &str, max_width: usize) -> String {