## What changed
Replace `AttachmentStore::persist` with `upload` and `resolve`. Uploads return inline bytes or a file ID; resolution returns optional file metadata and a download URL only when a minimum URL lifetime is requested. Add image dimensions, digest, size, MIME type, and categorized errors to the API.
Make `InlineAttachmentStore` return the original bytes and report `NotFound` when resolving file IDs. Redact attachment bytes and file URLs in debug output.
Pass the configured image store from the thread manager into sessions and inherit it in delegated sessions. Allow `TestCodexBuilder` to accept a custom image store.
## Testing
Update unit coverage for preserving PNG and JPEG bytes, redacting bytes and URLs in debug output, and rejecting file resolution in the inline store.
GitOrigin-RevId: f313e0048925998d84394c7e5a278e0d39d86a45
## What changed
- Add the `codex-attachment-store` crate with storage-neutral attachment metadata, references, errors, and an asynchronous persistence interface.
- Provide an inline implementation that preserves attachment bytes as media-typed base64 data URLs.
- Inject the store into `ThreadManager`, expose it to consumers, and retain inline storage as the default for existing entry points.
## Testing
- Verify inline storage round-trips binary, text, PNG, and JPEG data.
- Verify attachment debug output redacts URLs while retaining file IDs.
GitOrigin-RevId: 7688dcd3c89d7540ed2398f3e7c63881fbfcda97
Krish Chainani