feat(server): attachment embedding (#13348)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Added support for managing "blobs" in Copilot context, including
adding and removing blobs via new GraphQL mutations and UI fields.
* Introduced tracking and querying of blob embeddings within workspaces,
enabling search and similarity matching for blob content.
* Extended Copilot context and workspace APIs, schema, and UI to display
and manage blobs alongside existing documents and files.

* **Bug Fixes**
* Updated context and embedding status logic to handle blobs, ensuring
accurate status reporting and embedding management.

* **Tests**
* Added and updated test cases and snapshots to cover blob embedding
insertion, matching, and removal scenarios.

* **Documentation**
* Updated GraphQL schema and TypeScript types to reflect new
blob-related fields and mutations.

* **Chores**
* Refactored and cleaned up code to support new blob entity and
embedding logic, including renaming and updating internal methods and
types.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/models/common/copilot.ts

@@ -37,6 +37,11 @@ const ContextEmbedStatusSchema = z.enum([
   ContextEmbedStatus.failed,
 ]);
 
+const ContextBlobSchema = z.object({
+  id: z.string(),
+  createdAt: z.number(),
+});
+
 const ContextDocSchema = z.object({
   id: z.string(),
   createdAt: z.number(),
@@ -64,6 +69,9 @@ export const ContextCategorySchema = z.object({
 
 export const ContextConfigSchema = z.object({
   workspaceId: z.string(),
+  blobs: ContextBlobSchema.merge(
+    z.object({ status: ContextEmbedStatusSchema.optional() })
+  ).array(),
   files: ContextFileSchema.array(),
   docs: ContextDocSchema.merge(
     z.object({ status: ContextEmbedStatusSchema.optional() })
@@ -77,10 +85,9 @@ export const MinimalContextConfigSchema = ContextConfigSchema.pick({
 
 export type ContextCategory = z.infer<typeof ContextCategorySchema>;
 export type ContextConfig = z.infer<typeof ContextConfigSchema>;
+export type ContextBlob = z.infer<typeof ContextConfigSchema>['blobs'][number];
 export type ContextDoc = z.infer<typeof ContextConfigSchema>['docs'][number];
 export type ContextFile = z.infer<typeof ContextConfigSchema>['files'][number];
-export type ContextListItem = ContextDoc | ContextFile;
-export type ContextList = ContextListItem[];
 
 // embeddings
 
@@ -106,6 +113,10 @@ export type FileChunkSimilarity = ChunkSimilarity & {
   mimeType: string;
 };
 
+export type BlobChunkSimilarity = ChunkSimilarity & {
+  blobId: string;
+};
+
 export type DocChunkSimilarity = ChunkSimilarity & {
   docId: string;
 };