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-core/src/geometry-cache.ts

@@ -250,7 +250,8 @@ function evictOldestEntries(cacheDir: string, maxEntries: number): void {
       const fullPath = join(cacheDir, f)
       try {
         return { name: f, path: fullPath, mtime: statSync(fullPath).mtimeMs }
-      } catch {
+      } catch (err) {
+        console.warn(`[imhotep-core] cache eviction: stat failed for ${f}: ${err instanceof Error ? err.message : err}`)
         return null
       }
     })
@@ -262,8 +263,8 @@ function evictOldestEntries(cacheDir: string, maxEntries: number): void {
     for (let i = 0; i < toRemove; i++) {
       try {
         rmSync(files[i].path)
-      } catch {
-        // ignore deletion errors
+      } catch (err) {
+        console.warn(`[imhotep-core] cache eviction: failed to remove ${files[i].path}: ${err instanceof Error ? err.message : err}`)
       }
     }
   }
@@ -277,7 +278,8 @@ export async function readCachedWorld(cacheDir: string, cacheKey: string): Promi
   try {
     const json = await readFile(path, 'utf-8')
     return deserializeGeometryWorld(json)
-  } catch {
+  } catch (err) {
+    console.warn(`[imhotep-core] readCachedWorld failed for ${cacheKey}: ${err instanceof Error ? err.message : err}. Cache miss.`)
     return null
   }
 }
@@ -303,8 +305,8 @@ export function clearGeometryCache(cacheDir: string = DEFAULT_CACHE_DIR): void {
     if (file.endsWith('.json')) {
       try {
         rmSync(join(cacheDir, file))
-      } catch {
-        // ignore deletion errors
+      } catch (err) {
+        console.warn(`[imhotep-core] cache clear: failed to remove ${file}: ${err instanceof Error ? err.message : err}`)
       }
     }
   }
@@ -390,7 +392,8 @@ export async function readCachedExtractionResult(
   try {
     const json = await readFile(path, 'utf-8')
     return deserializeExtractionResult(json)
-  } catch {
+  } catch (err) {
+    console.warn(`[imhotep-core] readCachedExtractionResult failed for cacheKey=${cacheKey}: ${err instanceof Error ? err.message : err}. Cache miss.`)
     return null
   }
 }