fix: remove silent error suppression — cache failures, box index mutation, cleanup catches

geometry-cache.ts: replace 5 empty catch blocks with console.warn
- statSync failure, rmSync failure (x2), readCachedWorld failure,
  readCachedExtractionResult failure were all silently swallowed.
  Now emit context-bearing warnings so stale/corrupt caches are visible.

predicates.ts: replace __boxIndex as any mutation with WeakMap
- getBorderRect used (world as any).__boxIndex to cache a subject-to-
  box-index map on the world object. Replaced with module-level WeakMap
  that auto-collects when the world is GC'd. Eliminates 2 as any casts.

extraction.ts: serialize materializeSemanticSelector + debug cleanup
- 3 Promise.all sites over page.evaluate changed to sequential for..of
  to eliminate DOM modification race conditions.
- 2 .catch(()=>{}) cleanup blocks now use console.debug so failed
  cleanup is traceable when debugging.
- resolveViewport catch now emits console.warn on zero-viewport fallback.

648 SDK + 57 E2E tests pass.

packages/imhotep-solver/src/predicates.ts

@@ -166,17 +166,17 @@ export function getRequiredFactsForPredicate(name: string): string[] {
 // Built-in Predicate Evaluators
 // ---------------------------------------------------------------------------
 
+const boxIndexCache = new WeakMap<GeometryWorld, Map<number, number>>()
+
 function getBorderRect(world: GeometryWorld, subjectId: number) {
   const { boxes } = world;
-  // Build a subjectId -> boxIndex map on first use for O(1) lookups.
-  // This avoids O(n) linear scans on every predicate evaluation.
-  let index = (world as any).__boxIndex as Map<number, number> | undefined;
+  let index = boxIndexCache.get(world);
   if (!index) {
     index = new Map<number, number>();
     for (let i = 0; i < boxes.subjectId.length; i++) {
       index.set(boxes.subjectId[i], i);
     }
-    (world as any).__boxIndex = index;
+    boxIndexCache.set(world, index);
   }
   const i = index.get(subjectId);
   if (i === undefined) {