feat(web): state the run state on the terminal card's prompt line

The terminal card showed no run state: a running command and a settled
command that produced no output rendered the same prompt line, so whether
a command was still running had to be inferred from the absence of output.

Lead the prompt line with a StateDot in three of its states — the spinning
ring while running, red for the same exit status that renders the status
pill, green for a clean settle. That is the same indicator a tool row's
leading icon carries, so a row and its own card cannot disagree about one
command; the row/card agreement is pinned in the ui-conversation spec.
StateDot is aria-hidden, so a visually hidden text label rides beside it,
which is what the refreshed aria goldens now record.

The e2e adds what jsdom cannot compute: the dot's color resolves to the
green success token through the real theme stylesheet, and the dot precedes
the prompt label in document order.

packages/client/ui-primitives/src/TerminalBlock.module.css

@@ -36,6 +36,23 @@
   font: var(--dsw-font-markdown-code-block);
 }
 
+/* The dot sits on the prompt row's baseline box, which is a code-font line, so
+   it is centered against that line's box rather than sitting on the baseline. */
+.runState {
+  flex: none;
+  align-self: center;
+}
+
+/* The dot is aria-hidden; this is its text label for assistive technology. */
+.runStateLabel {
+  position: absolute;
+  width: 1px;
+  height: 1px;
+  overflow: hidden;
+  clip-path: inset(50%);
+  white-space: nowrap;
+}
+
 .cwd {
   flex: none;
   color: var(--dsw-alias-label-tertiary);