Fix capacity-overflow panic in print_snip at --terminal-width 1

`InteractivePrinter::print_snip` computes the snip separator width as
`term_width - panel_count - snip_left_count - title_count`. At `--terminal-width 1`
the panel is disabled and `title_count == 2`, so the subtraction underflows
`usize` (release has no overflow-checks, so it wraps to ~usize::MAX); `str::repeat`
then aborts with "capacity overflow" whenever a snip separator is emitted (two or
more disjoint line ranges, or a diff gap) — which the default style does.

Use `saturating_sub` for the repeat counts so they clamp to 0 instead of
underflowing. Added an integration test.

CHANGELOG.md

@@ -22,6 +22,7 @@
 - Syntax highlighting for Python files using uv as script runner in shebang #3689 (@janlarres)
 
 ## Bugfixes
+- Fix `capacity overflow` panic when printing a snip separator at `--terminal-width=1` with multiple line ranges. Closes #3803, see #3804 (@leeewee)
 - Pass `--no-paging` to `bat` invocations inside the bash / zsh / fish / PowerShell shell completion scripts so that shell-level pager wiring (e.g. `LESSOPEN='|-bat -f -pp %s'`) cannot inject ANSI escape sequences into the completion candidates. Closes #3760 (@mvanhorn)
 - Quote filenames before substituting them into `$LESSOPEN` / `$LESSCLOSE` templates, preventing shell injection when a filename contains shell metacharacters, see #3726 (@curious-rabbit)
 - Fix `--list-themes` unconditionally probing the terminal via OSC 10/11 even when `--theme` was set to an explicit value, see #3700 (regression introduced in bc42149a). (@optimistiCli)