feat(ui): separate dev info into a Diagnose view, declutter the scan workspace

Reworks the UI so the Scan tab shows only core actions and all developer /
diagnostic surfaces live in one dedicated view.

- New "Diagnose" nav view. ScanView stays mounted for scan|diagnose (the scan
  controller state persists across the switch) and renders either the clean
  workspace or the new DiagnosticsView by mode.
- DiagnosticsView consolidates runtime/rights, grid detection, learning + data
  staleness, fingerprint, auto-scan counters, the automation log, the dev-output
  toggle, the Demo-Daten action, and the raw crops/OCR/confidence dump. Reuses
  the existing diagnostics/details model hooks.
- Scan workspace decluttered: removed the Scanner Diagnose button and the Details
  button, dropped the rules/grid/mode dev fields from the result brief and capture
  meta, shortened the topbar headline, and moved Demo-Daten out of the topbar.
- Removed the now-dead ScanDiagnosticsModal / ScanDetailsModal components (their
  content moved into the view); metrics grid hidden on the Diagnose view.
- Added dev:web script + .claude/launch.json for browser preview.

Verified in the browser preview (both views render, no console errors); 120
tests + build green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/features/scan/components/ScanModalsSection.tsx

@@ -1,46 +1,27 @@
-import { ScanDiagnosticsModal } from "./modals/ScanDiagnosticsModal";
 import { ScanSettingsModal } from "./modals/ScanSettingsModal";
-import { ScanDetailsModal } from "./modals/ScanDetailsModal";
 import { ScanReviewQueueModal } from "./modals/ScanReviewQueueModal";
 import { ScanSummaryModal } from "./modals/ScanSummaryModal";
 import type { ScanModalsSectionProps } from "./types";
 
+// Diagnostics + crop/OCR details moved to the dedicated Diagnose view; only the
+// core workspace modals live here.
 export function ScanModalsSection({
-  captureStatus,
   latestCapture,
-  diagnosticsOpen,
   settingsOpen,
-  detailsOpen,
   reviewQueueOpen,
   controller,
-  setDiagnosticsOpen,
   setSettingsOpen,
-  setDetailsOpen,
   setReviewQueueOpen,
   setScanSummary,
 }: ScanModalsSectionProps) {
   return (
     <>
-      <ScanDiagnosticsModal
-        open={diagnosticsOpen}
-        captureStatus={captureStatus}
-        latestCapture={latestCapture}
-        controller={controller}
-        setDetailsOpen={setDetailsOpen}
-        setDiagnosticsOpen={setDiagnosticsOpen}
-      />
       <ScanSettingsModal
         open={settingsOpen}
         latestCapture={latestCapture}
         controller={controller}
         setSettingsOpen={setSettingsOpen}
       />
-      <ScanDetailsModal
-        open={detailsOpen}
-        latestCapture={latestCapture}
-        controller={controller}
-        setDetailsOpen={setDetailsOpen}
-      />
       <ScanReviewQueueModal
         open={reviewQueueOpen}
         controller={controller}