Introduce app_asset_contents table as a read-through cache over S3 for
text-like asset files (e.g. .md skill documents). This eliminates N
individual S3 fetches during SkillBuilder builds — bulk_load pulls all
content in a single SQL query with S3 fallback on miss.
Key components:
- CachedContentAccessor: DB-first read / dual-write / S3 fallback
- AssetContentService: static DB operations (get, get_many, upsert, delete)
- should_mirror(): single source of truth for extension-based policy
- Alembic migration for app_asset_contents table
Modified callers:
- SkillBuilder uses accessor.bulk_load() instead of per-node S3 reads
- AppAssetService.get/update_file_content route through accessor
- delete_node cleans both DB cache and S3
- draft_app_assets_initializer uses should_mirror() instead of hardcoded .md
- Updated API routes to use app_id instead of sandbox_id for file operations, aligning with user-specific sandbox workspaces.
- Enhanced SandboxFileService and related classes to accommodate app_id in file listing and download functionalities.
- Refactored storage key generation for sandbox archives to include app_id, ensuring proper file organization.
- Adjusted frontend contracts and services to reflect the new app_id parameter in API calls.
- Implemented the `exists` method in `SandboxFileSource` and its subclasses to verify the availability of sandbox sources.
- Updated `SandboxFileService` to utilize the new `exists` method for improved error handling when listing files and downloading files.
- Removed the previous check for storage existence in `archive_source.py` and replaced it with the new method.
- Replaced direct storage references with SilentStorage in various components to enhance fallback mechanisms.
- Updated storage key formats for sandbox archives and files to improve clarity and consistency.
- Refactored related classes and methods to utilize the new SandboxFilePath structure.
- Adjusted unit tests to reflect changes in the StorageTicket model and its serialization methods.
- Removed unused app asset download and upload endpoints, along with sandbox archive and file download endpoints.
- Updated imports in the file controller to reflect the removal of these endpoints.
- Simplified the generator.py file by consolidating the code context field definition.
- Enhanced the storage layer with a unified presign wrapper for better handling of presigned URLs.
