Raise the browser floors to Chrome 130, Firefox 132, and Safari 18

A floor applies to a whole major line. We cannot raise it in a minor
release, so whatever 6.0 ships caps what every later 6.x feature may use.
Earlier in this branch I set the floors on the first versions with native
`light-dark()`, which bought 2.18 points of coverage but left v6.x with
the oldest baseline we could tolerate rather than the one we want.

The low Firefox floor was also wrong on its own terms. `:has()` needs
Firefox 121, so Firefox 120 sat inside our support window and could not
render our forms, which use `:has()` 28 times in validation alone. The new
floors sit on the newest feature v6 already depends on: `:has()` at Firefox
121, `content-visibility` at Firefox 125 and Safari 18, `<details name>` at
Firefox 130, `text-wrap: balance` at Chrome 130, and unprefixed
`backdrop-filter` at Safari 18. `light-dark()` stays the hard lower bound.

Coverage drops from 87.19% to 85.01%. The JavaScript is byte-identical,
because every version in both sets handles the syntax we emit. The CSS
loses the `-webkit-backdrop-filter` copies on the Dialog and Drawer
backdrops, so it fits under the old bundlewatch limit again and this branch
no longer needs to raise it.

Author: mdo

.browserslistrc

@@ -6,7 +6,7 @@
 # because caniuse tracks Chrome for Android as one unversioned entry.
 #
 # Run `npx browserslist --coverage` for the real coverage figure. It reports
-# about 87% today. Do not read the number off browserslist.dev, because that
+# about 85% today. Do not read the number off browserslist.dev, because that
 # site pins an old caniuse-db and reports a different result.
 
 last 2 major versions
@@ -18,14 +18,24 @@ not dead
 # It costs nothing, because the version is newer than every floor below.
 unreleased versions
 
-# Floors sit on the first versions with native CSS `light-dark()` and nesting.
-# Below these versions Lightning CSS lowers `light-dark()` to a custom-property
-# polyfill, and that polyfill breaks `data-bs-theme` dark mode.
-Chrome >= 123
-Edge >= 123
-Firefox >= 120
-iOS >= 17.5
-Safari >= 17.5
+# These floors are the platform baseline for the whole v6.x line. We cannot raise
+# them in a minor release, so they cap what every future 6.x feature may use.
+# Each floor sits on the newest feature we already depend on, not the oldest one
+# we could tolerate:
+#   - `:has()` needs Firefox 121. We use it in forms, button groups and cards.
+#   - `content-visibility` needs Firefox 125 and Safari 18. The accordion
+#     transitions it with `allow-discrete`.
+#   - Unprefixed `backdrop-filter` needs Safari and iOS 18. Dialog and Drawer
+#     blur their `::backdrop`. Below 18, Autoprefixer adds `-webkit-` copies.
+#   - `text-wrap: balance` needs Chrome 130. We ship it as a utility.
+# `light-dark()` sets the hard lower bound (Chrome 123, Firefox 120, Safari 17.5).
+# Below it, Lightning CSS lowers `light-dark()` to a custom-property polyfill, and
+# that polyfill breaks `data-bs-theme` dark mode. Never go below that bound.
+Chrome >= 130
+Edge >= 130
+Firefox >= 132
+iOS >= 18.0
+Safari >= 18.0
 
 # Autoprefixer adds `-webkit-mask-*` for UC and QQ, and `-moz-column-gap` for
 # KaiOS. Those three engines hold under 0.8% of users between them, so we drop

.bundlewatch.config.json

@@ -26,7 +26,7 @@
     },
     {
       "path": "./dist/css/bootstrap.css",
-      "maxSize": "50.75 kB"
+      "maxSize": "50.5 kB"
     },
     {
       "path": "./dist/css/bootstrap.min.css",