docs: cap reference-page <pre> height so horizontal scrollbar stays in view

[nv-slang-bot]

Summary

Fixes shader-slang/slang#11262 — Reference doc page is missing a side scroll bar.

Root cause (verified live)

The reference pages render every overload of a function in a single <pre> block. On dense entries (e.g. linalg::CoopMat<...>.Load, 16+ overloads) that single <pre>:

• has overflow: auto already (Furo default — works correctly)
• scrollWidth: 2353px, clientWidth: 736px — content really does overflow horizontally
• offsetHeight: 5722px — the <pre> itself is multiple viewport heights tall

Because the inner horizontal scrollbar sits at the bottom of the 5722px-tall <pre>, it's well below the fold. A user reading the top of the signature list has no visible scrollbar to grab. This matches @jkwak-work's clarification in the issue thread:

"It appears that there is a scroll bar inside of the iframe. But when the iframe is bigger/longer than one page, you cannot reach the scroll bar; because it is on the next page."

Fix

Single CSS rule, scoped to body.core-module-reference-page:

body.core-module-reference-page article[role="main"] pre {
    max-height: 75vh;
}

The <pre> becomes its own scroll viewport at most 75vh tall, so both axes' scrollbars stay in view as the user reads. Long overload lists now scroll inside the <pre> instead of stretching the page vertically. Pages with short <pre> blocks are unaffected (it's a max, not a fixed height).

Verification

Injected the same rule into the live page in a real browser (Chromium) before committing. Same <pre>:

	Before fix	After fix
<pre> height	5722px	474.75px
H-scrollbar visible	no (below fold)	yes (in viewport)
V-scrollbar visible	n/a (page scroll only)	yes (in viewport)
Page reaches all signatures	yes (via page scroll)	yes (via inner scroll)

Scope

Only body.core-module-reference-page is affected — the rest of the docs site is untouched. If similar overflow issues exist on tutorials or guides, those should be addressed separately.

Test plan

• Verified the rule constrains the offending page (coopmat-04/load-0.html) by injection in a live browser; both scrollbars become reachable.
• Confirmed shorter reference pages (where the <pre> is naturally < 75vh) are unaffected — max-height doesn't shrink content shorter than its limit.
• Sphinx build via CI (CSS-only change, no syntax-sensitive constructs).