Retire BreakpointsTest's docblock reference to the deleted theme.css

Plan step 39 (part 5). Tailwind no longer clears its own breakpoint
scale anywhere in the stack, so the guard's rationale changes from "a
leftover sm: compiles to nothing" to "a browser drops the invalid
class or wrong-width rule just as silently" — the scans themselves
already worked over plain files and needed no change.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9

tests/Feature/BreakpointsTest.php

@@ -5,10 +5,12 @@ use Illuminate\Support\Facades\File;
 /**
  * Breakpoints are M3's window size classes and only those: compact below `medium`, then medium 600,
  * expanded 840, large 1200 and extra-large 1600 (docs/reference/m3/foundations.md § Layout,
- * foundations-supplement.md § Breakpoints). Tailwind's own screens are cleared in
+ * foundations-supplement.md § Breakpoints). Tailwind is gone from the whole stack (plan step 39),
- * resources/css/tokens/theme.css — `--breakpoint-*: initial` — so an `sm:` left behind compiles to
+ * so a leftover `sm:` class or a media query at one of its screen widths no longer compiles to
- * nothing at all and the rule it carried silently disappears. These two scans are the guard: one
+ * nothing — a browser just as silently ignores the invalid class or the wrong-width rule, so the
- * for the utilities, one for the media queries a stylesheet or a script writes by hand.
+ * mistake is exactly as easy to miss. These two scans are the guard: one for a Tailwind-shaped
+ * prefix (a habit, or an example pasted from elsewhere), one for the media queries a stylesheet or
+ * a script writes by hand.
  *
  * @return list<SplFileInfo>
  */