/**
 * Extended compatibility: OPT-IN module for old browsers. Call `compat()`
 * once, before anything else from scrollvars:
 *
 *   import { compat } from 'scrollvars/compat'
 *   compat()
 *
 * On a modern browser it runs three feature checks and returns false. No
 * stubs, no styles, effectively free. On an old one it patches the gaps:
 *
 *   - ResizeObserver missing (Safari < 13.1): a window-resize-backed stub:
*     re-measures on viewport changes (misses pure content growth; the page
 *     still works, call `refresh()` after big DOM swaps if needed). Its
 *     `contentRect` is measured from the layout box, like the native
 *     observer, so an ancestor `transform: scale()` never inflates it.
 *   - IntersectionObserver missing (Safari < 12.1): an always-visible stub:
*     the canvas harness simply never auto-pauses offscreen.
 *   - Individual transform properties missing (`translate:`, Chrome < 104,
 *     Firefox < 72, Safari < 14.1): injects a fallback stylesheet that
 *     re-expresses with `transform:` the same presets README lists:
 *     sv-rise, sv-fade, sv-slide-l, sv-slide-r, sv-auto (its auto-ordered
 *     children), sv-drift, sv-curtain-l, sv-curtain-r, sv-rail.
 *     Written without :is(), clamp() or min() so the old parser accepts
 *     it; the one max() left, drift's fade, sits behind a plain opacity
 *     declaration that parser keeps. Two presets stay static, one
 *     reason each:
 *       sv-deck, unstacked here to a static, non-overlapping layout
 *         because its fly-away slice needs clamp();
 *       sv-spread, no fallback rule, its selector parses fine and
 *         there is simply no translate/rotate left to apply.
 *     sv-split-rise has no fallback rule either, but its floor is not
 *     one line: below :is() support the rule is dropped whole and it
 *     is fully static, above it the opacity declaration still
 *     transitions, so it fades in without rising.
 *     sv-reading falls back to fully-visible text; sv-counter and
 *     sv-view-* stay progressive.
 *     Installing the sheet also marks <html> with data-sv-compat: the pin
 *     presets above animate from --sv-pin, so styles/pin.css keeps the
 *     stage pinned and the driver keeps writing the tall wrapper height
 *     instead of releasing both, which is what a page with no compat()
 *     wants down here.
 *
 * Syntax floor stays the consumer's job: the dist ships ES2020; if you must
 * PARSE on very old engines, let your bundler downlevel it (Next.js already
 * transpiles per browserslist via transpilePackages).
 */
/** Apply the patches this browser needs. Returns true if anything was patched. */
export declare function compat(): boolean;