Fix cache lookup to work across processes

cache_manager.py:
- get_by_content_hash() now tries direct cache.get(content_hash)
  since uploads use content_hash as node_id
- This works even if cache index hasn't been reloaded

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cache_manager.py

@@ -250,6 +250,14 @@ class L1CacheManager:
             if path and path.exists():
                 return path
 
+        # For uploads, node_id == content_hash, so try direct lookup
+        # This works even if cache index hasn't been reloaded
+        path = self.cache.get(content_hash)
+        if path and path.exists():
+            self._content_index[content_hash] = content_hash
+            self._save_content_index()
+            return path
+
         # Scan cache entries (fallback for new structure)
         entry = self.cache.find_by_content_hash(content_hash)
         if entry and entry.output_path.exists():