feat(demo): make return, data-quality and knowledge flows demo-legible

Fixes a real honesty bug in Knowledge.tsx (body copy named "RAGcore" while
the active provider is the demo one) and a second real bug discovered
while fixing it: the brief's suggested Dutch questions would silently
return "insufficient evidence" against the English-only demo knowledge
base -- verified empirically and fixed by keeping suggested questions in
English. The return flow now pre-fills the odometer-regression scenario's
suspicious reading instead of asking a visitor to invent one, and links
to automation/audit after committing. Data-quality issues get a shared
plain-language "what's wrong / why it matters" explainer per rule type,
a post-resolution confirmation with audit/vehicle links, and a "demo
scenario's only" list filter. Also fixes a real async race where the
odometer pre-fill could clobber text a visitor had already started typing.

frontend/src/styles.css

@@ -248,6 +248,14 @@ details summary { cursor: pointer; color: var(--teal-dark); }.data-table details
 .impact-preview { display: flex; align-items: flex-start; gap: 11px; padding: 15px; border: 1px solid; border-radius: var(--radius); }.impact-preview > svg { width: 20px; flex: 0 0 auto; }.impact-preview strong { font-size: .76rem; }.impact-preview p { margin: 4px 0 0; font-size: .72rem; line-height: 1.45; }.impact-ready { color: #185d41; background: var(--success-pale); border-color: #bfe3d0; }.impact-warning { color: #844909; background: var(--warning-pale); border-color: #eed4aa; }
 .commit-list { list-style: none; display: grid; gap: 7px; margin: 16px 0 0; padding: 0; color: var(--muted); font-size: .7rem; }.commit-list li { display: flex; gap: 7px; }.commit-list svg { width: 14px; color: var(--teal-dark); }
 .success-panel { padding: 22px; }.result-heading { display: flex; align-items: center; gap: 12px; margin-bottom: 18px; }.result-heading > span { width: 40px; height: 40px; display: grid; place-items: center; color: white; background: var(--success); border-radius: 50%; }.result-heading svg { width: 20px; }.result-heading h2 { margin: 0; font-size: 1.2rem; }
+.result-links { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 16px; }
+.rule-explainer { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 14px; margin-bottom: 18px; padding: 16px 18px; background: var(--info-pale); border: 1px solid #cfe3ee; border-radius: var(--radius); }
+.rule-explainer strong { display: block; margin-bottom: 4px; color: var(--ink); font-size: .72rem; font-weight: 700; text-transform: uppercase; letter-spacing: .05em; }
+.rule-explainer p { margin: 0; color: var(--ink-soft); font-size: .78rem; line-height: 1.55; }
+.scenario-callout { display: flex; align-items: flex-start; gap: 12px; margin-bottom: 18px; padding: 16px 18px; background: var(--teal-pale); border: 1px solid #bfe6df; }
+.scenario-callout svg { width: 18px; height: 18px; color: var(--teal-dark); flex-shrink: 0; margin-top: 2px; }
+.scenario-callout strong { display: block; margin-bottom: 4px; color: var(--ink); font-size: .82rem; }
+.scenario-callout p { margin: 0; color: var(--ink-soft); font-size: .78rem; line-height: 1.55; }
 
 .duplicate-compare { margin-top: 18px; }.duplicate-compare fieldset { margin: 15px 0; padding: 13px; border: 1px solid var(--line); }.duplicate-compare legend { padding: 0 5px; color: var(--ink-soft); font-size: .69rem; font-weight: 700; }.duplicate-compare fieldset label { display: inline-flex !important; margin-right: 18px; }
 .compare-table th, .compare-table td { vertical-align: top; }.compare-table label { display: inline-flex; flex-direction: row; align-items: center; gap: 6px; }.difference-mark, .match-mark { display: block; width: max-content; margin-top: 4px; padding: 2px 5px; font-size: .52rem; border-radius: 2px; }.difference-mark { color: var(--warning); background: var(--warning-pale); }.match-mark { color: var(--success); background: var(--success-pale); }
@@ -293,6 +301,14 @@ details summary { cursor: pointer; color: var(--teal-dark); }.data-table details
   .app-shell { grid-template-columns: 190px minmax(0, 1fr); }.sidebar { width: 190px; }.brand-lockup { padding-inline: 14px; }.readiness-band { grid-template-columns: 160px 1fr; }.readiness-band .inline-action { display: none; }.operations-grid { grid-template-columns: 1fr 1fr; }.timezone { display: none; }.review-facts { grid-template-columns: repeat(3, 1fr); }
 }
 
+.knowledge-provider-note { display: flex; align-items: flex-start; gap: 8px; margin: -6px 0 18px; padding: 10px 14px; color: var(--ink-soft); background: var(--info-pale); border: 1px solid #cfe3ee; border-radius: var(--radius); font-size: .72rem; line-height: 1.5; }
+.knowledge-provider-note svg { width: 15px; flex-shrink: 0; margin-top: 1px; color: var(--info); }
+.knowledge-suggestions { display: flex; flex-wrap: wrap; align-items: center; gap: 7px; margin-top: 12px; }
+.knowledge-suggestions > span { color: var(--muted); font-size: .68rem; font-weight: 700; }
+.suggestion-chip { padding: 6px 11px; color: var(--teal-dark); background: var(--teal-pale); border: 1px solid #bfe6df; border-radius: 999px; font-size: .68rem; font-weight: 600; cursor: pointer; }
+.suggestion-chip:hover { background: #d9f0ea; }
+.suggestion-chip:disabled { opacity: .6; cursor: not-allowed; }
+
 .demo-start-panel { display: flex; align-items: center; justify-content: space-between; gap: 16px; flex-wrap: wrap; margin-bottom: 22px; padding: 16px 20px; background: var(--teal-pale); border: 1px solid #bfe6df; border-radius: var(--radius); }
 .demo-start-panel > div:first-child { display: flex; align-items: center; gap: 12px; }
 .demo-start-panel > div:first-child > svg { width: 22px; height: 22px; color: var(--teal-dark); flex-shrink: 0; }