`aria-*` boolean attributes serialize as the empty string

• Where: every aria: {hidden: true}, aria_disabled: true,
  aria_expanded: true in the catalog — breadcrumb separators and ellipsis,
  CommandInput, and every decorative <svg aria-hidden>. Snapshots carry
  aria-hidden="", aria-disabled="", aria-expanded="".
• Effect: the ARIA value grammar accepts true/false/undefined; an
  empty string is invalid and browsers resolve it as not set. Decorative
  icons are therefore exposed to assistive technology, "current" breadcrumb
  items are not announced as disabled, and the command input's expanded
  state is unset. This is Phlex's serialization of true (a bare
  attribute), so it is library-wide, not one component.
• Fix: pass "true" (a String) for aria-* attributes, or add a
  serialization rule in Base that stringifies booleans under the aria
  key; re-record (on the 2.0 line) everything that changes and review the diff.
• 2.0 note: spec §4.3 currently preserves this behaviour for parity
  (true → ""). The right 2.0 behaviour is aria-x="true"; decide it
  explicitly and let the re-record (on the 2.0 line) show the blast radius.

Surfaced by the golden HTML suite (PR #536), which pins what 1.6 renders today — this defect included. Per maintainer decision (2026-09-19) main stays as is: this is addressed on the 2.0 line, and the golden snapshot that pins it is re-recorded there with the diff reviewed.

Source: design/v2/follow-up-issues.md.

Lies design/v2/follow-up-issues.md und untersuche den Base-Serialisierungspfad für aria-Attribute im 2.0-Zweig. Führe die golden HTML suite aus und prüfe die betroffenen Katalog- und Komponenten-Snapshots, einschließlich Breadcrumb-Trennzeichen, Ellipse, CommandInput und dekorativer SVGs. Erledigt ist die Aufgabe, wenn aria-Boolesche Werte wie festgelegt als "true" oder "false" gerendert werden, die 2.0-Snapshots neu aufgezeichnet wurden und ihr Diff geprüft wurde.