fix(themes): cap narrow-viewport sidebar and restore aside selectors (#8749)
* fix(themes): tighten narrow-viewport sidebar with Material drawer cap
Cap `.aside.visible` width at `min(var(--width-aside, 320px), calc(100vw - 56px))` instead of 90%. Themes that define `--width-aside` (Swage) keep their existing value; others get a 320px cap with a 56px touch peek of the underlying view.
Also restores aside selectors dropped by recent refactors:
- #8201 renamed `.aside:target` to `.aside.visible` in base-theme; this fix applies the same rename in Swage, Nord, Origine, and Alternative-Dark
- #8200 dropped Swage's narrow-viewport sidebar width override; the new base cap covers that case for Swage and the other themes equally
- Nord's `max-width: 300px` aside override is now redundant with the base cap and is removed
* fix(themes): merge duplicate .aside.visible rule
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Co-authored-by: Bjørn A. Andersen <polybjorn@users.noreply.github.com>