Unify capture/edit form, thicker active document border, layer-hide toggles

Three UX iterations rolled into one:

1. Unified evidence form
   - New EvidenceFormBody is the single source for "citation +
     commentary" editing. Both InlineCaptureForm (creating fresh
     evidence from a selection) and the EvidenceCard edit mode render
     this body with their own save/cancel labels + badge/helper text.
   - The capture form now exposes the citation as an editable
     textarea — pre-filled with the selection text — so the user can
     refine a partial capture before saving without re-selecting.
   - Old testid prefixes are unchanged for the inline-capture flow
     (`inline-capture-quote/commentary/save/cancel`); edit-mode
     testids are now `evidence-edit-<id>-{quote,commentary,save,cancel}`.

2. Active document card
   - The blue background alone was the only "this is open" cue. Added
     a 3px #0050b3 border (matching the evidence-card thick-border
     pattern, but in the documents-are-blue palette) plus a
     `data-active` attribute.

3. PDF layer-hide diagnostics
   - New debug flags `hideCanvas`, `hideTextLayer`, `hideAnnotationLayer`,
     `hideXfaLayer` — applied as `.ce-hide-<layer>` classes on the viewer
     wrapper, each `display: none`-ing the matching PDF.js layer.
   - SessionMenu groups the toggles under a "PDF diagnostics" header
     with a new shared DebugCheckbox helper. The existing "Debug text
     layer" highlight toggle now lives in the same group.
   - Lets the user isolate stacking issues by elimination — e.g.
     "hide text layer, can I now see the canvas content underneath?".

Tests
   - citation-card-export-e2e + session-export-reimport switched from
     placeholder/role-name lookups to the inline-capture testids so
     they survive form-copy changes.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/work/ViewerShell.tsx

@@ -32,6 +32,10 @@ export function ViewerShell() {
   const { set: setPending } = usePendingSelection();
   const { id: scrollToId, version: scrollVersion, scrollTo } = useScrollToAnnotation();
   const [debugTextLayer] = useDebugFlag("textLayer");
+  const [hideCanvas] = useDebugFlag("hideCanvas");
+  const [hideTextLayer] = useDebugFlag("hideTextLayer");
+  const [hideAnnotationLayer] = useDebugFlag("hideAnnotationLayer");
+  const [hideXfaLayer] = useDebugFlag("hideXfaLayer");
   const activeEvidenceId = useLastActivatedEvidence();
 
   // The viewer needs to re-fetch its highlight list whenever annotations
@@ -108,16 +112,29 @@ export function ViewerShell() {
     >
       <div style={{ flex: 1, overflow: "hidden", position: "relative" }}>
         <PdfSpikeViewer
-          // Re-key on scrollVersion so clicking the same item twice still
-          // triggers the viewer's mount-time scroll effect. Also re-key on
-          // debugTextLayer so toggling it remounts the viewer.
-          key={`${document.id}#${scrollVersion}#${debugTextLayer ? "d" : "n"}`}
+          // Re-key on scrollVersion + debug flags so toggling any of
+          // them remounts the viewer (the CSS classes are on a parent,
+          // but a re-render is the simplest way to make sure the layers
+          // get re-laid-out).
+          key={[
+            document.id,
+            scrollVersion,
+            debugTextLayer ? "d" : "n",
+            hideCanvas ? "hc" : "",
+            hideTextLayer ? "ht" : "",
+            hideAnnotationLayer ? "ha" : "",
+            hideXfaLayer ? "hx" : "",
+          ].join("#")}
           pdfUrl={fileUrl}
           storedAnnotations={annotations}
           {...(scrollToId ? { scrollToAnnotationId: scrollToId } : {})}
           activeAnnotationId={activeAnnotationId}
           onHighlightClicked={handleHighlightClicked}
           debugTextLayer={debugTextLayer}
+          hideCanvas={hideCanvas}
+          hideTextLayer={hideTextLayer}
+          hideAnnotationLayer={hideAnnotationLayer}
+          hideXfaLayer={hideXfaLayer}
           onSelectionCaptured={(capture, selectors) => {
             setPending({ capture, selectors });
           }}