answered quiz cards show the confidence rail — the slider's record form

The rail paint is extracted to components/confidence-rail.tsx (ramp,
tick stack, geometry laws) and shared by both surfaces so they cannot
drift: the dock's live slider paints the rail under its disc, the
answered card renders it disc-less — the missing handle itself says
'record, not control'. Same look otherwise: thin rail, stop color,
solid ticks, % read-out on the right, dock-mirrored placement (below
the options, above the thinking).

Renders only where a confidence exists: quiz answers with one sent;
never on 'I don't know' (none was sent), never on explain/ask, never
on pre-feature records (optional field, absent).

components/answered-card.tsx

@@ -1,5 +1,6 @@
 "use client";
 
+import { ConfidenceRail } from "@/components/confidence-rail";
 import { GlyphMark } from "@/components/ui/glyph-mark";
 import { cn } from "@/lib/utils";
 import { MessageResponse } from "@/components/ai-elements/message";
@@ -101,6 +102,22 @@ export function AnsweredCard({ answer }: { answer: QuestionAnswerData }) {
 			)}
 
 			{answer.text && <div className="lh-prose mt-2 whitespace-pre-wrap">“{answer.text}”</div>}
+
+			{/* The confidence record (owner round 6): the slider's rail, disc
+			    removed — the missing handle itself says "this is a record, not a
+			    control". Same paint, same ticks, same ramp, same % read-out as the
+			    live dock. Quiz answers only, and only when a confidence exists:
+			    "I don't know" sent none (its slider was grayed out), explain and
+			    ask never had one, and records from before the feature carry no
+			    field — nothing to show, nothing rendered. */}
+			{isQuiz && answer.confidence != null && (
+				<div className="mt-3 flex items-center gap-3" data-testid="answered-confidence">
+					<ConfidenceRail value={answer.confidence} className="min-w-0 flex-1" />
+					<span className="w-9 shrink-0 text-right font-mono text-sm tabular-nums text-muted-foreground">
+						{answer.confidence}%
+					</span>
+				</div>
+			)}
 			{answer.dontKnow && isQuiz && (
 				<div className="mt-2 text-sm text-muted-foreground">Answered “I don't know”.</div>
 			)}