feat(parse): report per-sheet recognition and block error sheets

- parseWorkbook returns a report per sheet (table counts, issues, ok)
- sheets with E-level issues cannot be selected (spec section 2.3)
- pier input carries its source sheet name

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>

src/style.css

@@ -216,6 +216,11 @@ td:first-child {
   color: var(--warn);
 }
 
+.issues .sheet-ok {
+  font-weight: 600;
+  color: var(--primary);
+}
+
 @media (max-width: 900px) {
   .layout {
     grid-template-columns: 1fr;