`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.

design/v2/follow-up-issues.md を読み、2.0 系列の aria 属性に関する Base のシリアライゼーションパスを調査してください。golden HTML suite を実行し、影響を受けるカタログとコンポーネントのスナップショットを確認してください。breadcrumb の区切り、ellipsis、CommandInput、装飾的な SVGs も対象に含めます。完了条件は、aria のブール値が決定どおり "true" または "false" としてレンダリングされ、2.0 のスナップショットが再記録され、その diff がレビューされていることです。