fix(coach): collapse the evidence disclosure to closed-by-default

The assistant bubble's evidence `<details>` mounted open whenever the
user had `coachPrefs.showEvidenceByDefault = true`, which surfaced the
raw measurement values (e.g. "Blutdruck letzte 30 Tage: 226") under
every reply. The disclosure is now always collapsed; the user expands
by click. The persisted pref stays in the schema for backward
compatibility but no UI reads or writes it, so the value is dead-code-
tolerated for one release and can be dropped in the next migration.

Drops the `evidenceDefaultOpen` prop wiring from `<MessageThread>` and
the corresponding `<Switch>` in the Coach settings sheet. Adjusts the
sheet test that previously asserted the toggle was rendered.

src/components/insights/coach-panel/__tests__/coach-settings-sheet.test.tsx

@@ -91,7 +91,8 @@ describe("<CoachSettingsSheet>", () => {
     );
     expect(html).not.toContain('data-slot="coach-prefs-skeleton"');
     expect(html).toContain('data-slot="coach-prefs-tone"');
-    expect(html).toContain('data-slot="coach-prefs-evidence"');
+    // v1.4.27 F14 — the `showEvidenceByDefault` switch is retired.
+    expect(html).not.toContain('data-slot="coach-prefs-evidence"');
   });
 
   it("fires a sonner toast on save success (Design-H4)", () => {

src/components/insights/coach-panel/coach-settings-sheet.tsx

@@ -323,31 +323,13 @@ export function CoachSettingsSheet({
               </ul>
             </div>
 
-            {/* Show evidence by default */}
-            <div className="flex items-start justify-between gap-3">
-              <div className="flex flex-col gap-1">
-                <Label
-                  htmlFor="coach-prefs-evidence"
-                  className="cursor-pointer text-xs font-medium"
-                >
-                  {t("insights.coach.settingsEvidenceLabel")}
-                </Label>
-                <p className="text-muted-foreground text-[11px] leading-relaxed">
-                  {t("insights.coach.settingsEvidenceHint")}
-                </p>
-              </div>
-              <Switch
-                id="coach-prefs-evidence"
-                data-slot="coach-prefs-evidence"
-                checked={draft.showEvidenceByDefault}
-                onCheckedChange={(next) =>
-                  setDraft((prev) => ({
-                    ...prev,
-                    showEvidenceByDefault: next,
-                  }))
-                }
-              />
-            </div>
+            {/* v1.4.27 F14 — the `showEvidenceByDefault` switch was
+                retired. The evidence disclosure is now always closed
+                by default and the user expands by click; surfacing
+                raw values automatically created an UX trap. The
+                persisted `coachPrefs.showEvidenceByDefault` field
+                stays in the schema for backward compatibility, but no
+                UI reads or writes it. */}
           </div>
         )}
 

src/components/insights/coach-panel/message-thread.tsx

@@ -15,7 +15,6 @@ import { cn } from "@/lib/utils";
 import { useTranslations } from "@/lib/i18n/context";
 import { stripChartTokens } from "@/lib/insights/chart-tokens";
 import { useAuth } from "@/hooks/use-auth";
-import { useCoachPrefs } from "@/hooks/use-coach-prefs";
 
 import { SourceChips } from "./source-chips";
 import type {
@@ -105,13 +104,13 @@ export function MessageThread({
   const scrollerRef = useRef<HTMLDivElement | null>(null);
   const wasPinnedRef = useRef(true);
 
-  // v1.4.23 H4 — read the user's Coach prefs so the evidence
-  // disclosure honours `showEvidenceByDefault`. Cached at the
-  // queryClient level via the shared `useCoachPrefs` hook; the
-  // settings sheet writes the same key after a successful save so the
-  // new default takes effect on the next reply without a page reload.
-  const { data: coachPrefs } = useCoachPrefs();
-  const evidenceDefaultOpen = coachPrefs?.showEvidenceByDefault ?? false;
+  // v1.4.27 F14 — the evidence disclosure used to honour an opt-in
+  // `coachPrefs.showEvidenceByDefault` flag that surfaced the raw
+  // measurement values unconditionally. The flag created an UX trap
+  // (Marc 2026-05-15: "literal metric values exposed under every
+  // bubble") so the disclosure is now collapsed by default for every
+  // reply. The user expands by click; the pref is retired in the
+  // settings sheet so nothing flips it back on.
 
   const messages: CoachMessageDTO[] = useMemo(
     () => conversation?.messages ?? [],
@@ -239,7 +238,6 @@ export function MessageThread({
             content={m.content}
             metricSource={m.metricSource}
             providerType={m.providerType}
-            evidenceDefaultOpen={evidenceDefaultOpen}
             messageId={m.id}
           />
         );
@@ -269,7 +267,6 @@ export function MessageThread({
             providerType={streaming.inProgress ? "streaming" : null}
             inProgress={streaming.inProgress}
             errorCode={streaming.errorCode}
-            evidenceDefaultOpen={evidenceDefaultOpen}
           />
         </div>
       )}
@@ -299,8 +296,6 @@ interface ChatBubbleProps {
   providerType?: string | null;
   inProgress?: boolean;
   errorCode?: string | null;
-  /** v1.4.23 H4 — when true the evidence `<details>` mounts open. */
-  evidenceDefaultOpen?: boolean;
   /**
    * v1.4.23 H7 — present only on persisted assistant messages.
    * Streaming bubbles (no message id yet) skip the thumbs row so the
@@ -316,7 +311,6 @@ function ChatBubble({
   providerType,
   inProgress,
   errorCode,
-  evidenceDefaultOpen,
   messageId,
 }: ChatBubbleProps) {
   const { t } = useTranslations();
@@ -428,11 +422,11 @@ function ChatBubble({
         {keyValues.length > 0 && (
           <details
             data-slot="coach-evidence"
-            // v1.4.23 H4 — open by default when the user's prefs ask
-            // for it. Browsers honour the boolean `open` attribute on
-            // initial mount; toggling at runtime keeps the user's
-            // current expansion state intact.
-            open={evidenceDefaultOpen ? true : undefined}
+            // v1.4.27 F14 — always closed by default. The `open`
+            // attribute was previously tied to a per-user pref that
+            // surfaced raw values unconditionally; that pref is now
+            // retired and the disclosure is a true progressive-
+            // disclosure surface — the user clicks to expand.
             className={cn(
               "border-border/50 bg-muted/30 group rounded-md border",
               "px-2.5 py-1.5 text-xs",