v0.20.0

Agent UI building blocks and workspace

• Shared motion, reduced-motion policy and six-state status glyphs.
• Semantic result blocks, facts, checks, documents and collapsed run summaries.
• Extended streaming contracts, NDJSON decoding, completeness tracking, safe
  approval outcomes, intent-based scrolling and an IME-aware composer.
• Persistent multi-conversation workspace with responsive side drawers.
• Separate developer call console and server-only redacted HTTP/SSE call logging.

See agent UI contracts and
composition guidelines. Addresses #242–#251.

box-progress-bar stopped saying everything twice

The bar wrapped itself in a role="group" named `${label} progress`, while
the element actually carrying the progressbar role was named label. Two
consequences, both audible:

• the name was announced twice, once per element
• it stuttered, because the suffix was appended whether or not the label already
  ended in that word. The default label is Progress, so an unlabelled bar
  announced "Progress progress"; the uploader's rows announced
  "Foo.pdf upload progress progress"

The wrapper is now an unnamed layout element. The name lives on [part="track"]
and nowhere else, verbatim.

A progress bar can drop its visible label

New hide-label attribute (hideLabel property), for a bar sitting under
something that already names it. The label stays the accessible name; only the
visible copy goes. The percentage still renders.

Unlike the form fields' hide-label, this hides the label outright rather than
clipping it into a screen-reader-only box. There the label element is the
control's accessible name and has to stay readable; here the name is on the
track, so a clipped copy would only be read twice.

box-content-uploader uses it. Its rows showed the filename, then rendered
FOO.PDF UPLOAD PROGRESS again directly beneath — the uploader baseline is
shorter by one line per row because of it.

A side effect worth knowing about, since it applies to any bar you hide the
label on: [part="meta"] is a space-between flex row, so with the label gone
the percentage is its only child and moves from the far right to the start. In
the uploader that is an improvement — the figure was pushed out to the edge of
the row, and now sits under the filename it belongs to.

box-run-trace had been working around the same duplication by hiding the whole
meta line in CSS; its labels are corrected too, with no visual change.