Test check (iii) and fix two bugs it exposed in the application-CSS scan

Plan step 41(iii): fixtures/tests for every literal kind (colour, radius,
shadow, font size/weight, line height, letter spacing, easing, duration) and
an off-scale media query, plus material-scheme.css excluded by name and by
its generated header wherever it sits among the scanned paths. Also adds a
fixture proving Tailwind-shaped bare words in running prose are never read
as classes.

Two fixes found by writing the fixtures rather than only the implementation:
a directly-scanned .css file was also running through the Blade/PHP/JS checks
(the same file's `ease-in-out` in a `transition` value tripped the old scale
check a second time), so a CSS file is now check (iii)'s alone; and
`withoutTokenFunctions()` leaves a `var()`/`calc()` call's own name and
parentheses standing once its arguments are blanked, which
`isSafeLiteralValue()` did not yet recognise as the same "nothing to see
here" as an empty value.

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

tests/Fixtures/design-guard/app-css/app.css

@@ -0,0 +1,25 @@
+/* comments are ignored */
+.card {
+    color: #ff0000;
+    background: rgb(0, 0, 0);
+    border-radius: 12px;
+    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
+    font-size: 14px;
+    font-weight: 600;
+    line-height: 1.4;
+    letter-spacing: 0.02em;
+    transition: opacity 200ms ease-in-out;
+}
+
+.fine {
+    border-radius: var(--md-sys-shape-corner-lg);
+    color: var(--md-sys-color-primary);
+    padding: calc(var(--md-sys-measurement-space100) * 2);
+    border: 0;
+}
+
+@media (min-width: 700px) {
+    .card {
+        display: flex;
+    }
+}

tests/Fixtures/design-guard/app-css/generated-scheme.css

@@ -0,0 +1,7 @@
+/*
+ * Material 3 colour roles, generated by Google's material-color-utilities (spec 2025).
+ */
+
+:root {
+    --md-sys-color-primary: #6750a4;
+}

tests/Fixtures/design-guard/app-css/material-scheme.css

@@ -0,0 +1,3 @@
+:root {
+    --md-sys-color-primary: #6750a4;
+}