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

阅读 design/v2/follow-up-issues.md，并检查 2.0 版本中 aria 属性的 Base 序列化路径。运行 golden HTML suite，并检查受影响的目录和组件快照，包括 breadcrumb 分隔符、省略号、CommandInput 和装饰性 SVG。完成的标准是：aria 布尔值按决定渲染为 "true" 或 "false"，2.0 快照已重新记录，并且其 diff 已经过审查。

• Where: the components that pass a boolean under the aria hash:
  aria: {hidden: true} in BreadcrumbSeparator, BreadcrumbEllipsis and
  PaginationEllipsis (also reached through DataTablePagination),
  aria: {disabled: true} in BreadcrumbPage, aria_expanded: true in
  CommandInput. The breadcrumb, pagination, data_table and command
  snapshots carry aria-hidden="", aria-disabled="" or aria-expanded="".
  Components that pass the String "true" — InputOtpSlot,
  NativeSelectIcon, AlertDialogContent — already serialize correctly and
  are not affected.
• Effect: the ARIA value grammar accepts true/false/undefined; an
  empty string is invalid and browsers resolve it as not set. The breadcrumb
  and pagination separators and ellipses 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 under a nested hash (a bare attribute), so any component that passes
  a boolean there is affected — five today.
• 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.