Leave a Markdown mail component's classes to the mail theme in the design guard

A mail component is drawn by the mail theme, not by the application's
CSS entry, and the theme's classes share Tailwind's names: ReStride's
`x-mail::sessions` wraps its table in `<div class="table">`, the class
the package's own mail theme styles, and the guard reported it as
Tailwind's `display: table`. A view under a path `mail.markdown.paths`
names (Laravel's `resources/views/vendor/mail` by default) now skips
family (i) and the breakpoint, scale, palette and colour-value checks;
its icon names, the directives in its component tags, forbidColours()
and forbid() are still read. A mail theme stylesheet under that path,
which has to write literal values, is left out of check (iii) and of
the exempt classes, so its `.table` no longer hides `table` in the
application's other views either. The guard's docblock, the README and
the skill's "Testing the design" say so; a fixture test reads the same
mail view and theme with and without the path configured.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/Fixtures/design-guard/mail/views/page.blade.php

@@ -0,0 +1 @@
+<div class="table"></div>

tests/Fixtures/design-guard/mail/views/vendor/mail/html/sessions.blade.php

@@ -0,0 +1,8 @@
+@props(['sessions', 'url'])
+<div class="table">
+<table class="sessions text-sm" width="100%" cellpadding="0" cellspacing="0" role="presentation">
+<tr><td class="break-all">{{ $sessions }}</td></tr>
+</table>
+</div>
+<x-mail::button :url="$url" icon="not_a_symbol">Open the week</x-mail::button>
+<x-mail::panel @class(['wide'])>A panel</x-mail::panel>

tests/Fixtures/design-guard/mail/views/vendor/mail/html/themes/default.css

@@ -0,0 +1,4 @@
+.table th {
+    color: #3d4852;
+    font-size: 14px;
+}