Add web multimodal image attachments

packages/attachment/attachment/src/index.ts

@@ -0,0 +1,51 @@
+/** Durable attachment storage seam (`ctx.attachments`). @module @deepseek-ai/dsh-attachment */
+
+import { Context, Service } from 'cordis'
+import type {
+  ImageAttachmentLimits,
+  ImageAttachmentRef,
+  SaveImageAttachment,
+  StoredImageAttachment,
+} from './types.ts'
+
+export { AttachmentError, AttachmentId } from './types.ts'
+export type {
+  AttachmentId as AttachmentIdType,
+  ImageAttachmentLimits,
+  ImageAttachmentRef,
+  ImageMediaType,
+  SaveImageAttachment,
+  StoredImageAttachment,
+} from './types.ts'
+
+declare module 'cordis' {
+  interface Context {
+    attachments: AttachmentStore
+  }
+}
+
+/** Immutable binary attachment service. Implementations validate bytes before publishing a reference. */
+export abstract class AttachmentStore extends Service {
+  constructor(ctx: Context) {
+    super(ctx, 'attachments')
+  }
+
+  /** Deployment-resolved image policy used by authoritative and fast-path validation. */
+  abstract readonly imageLimits: ImageAttachmentLimits
+
+  /**
+   * Validate and durably commit one image before its owning session event is appended.
+   * @param input - encoded bytes, declared media type, and optional display name.
+   * @returns a durable content-addressed reference.
+   */
+  abstract saveImage(input: SaveImageAttachment): Promise<ImageAttachmentRef>
+
+  /**
+   * Read one image and verify that bytes still match the recorded reference.
+   * @param ref - durable reference from the session log.
+   * @returns the verified bytes and canonical reference.
+   */
+  abstract readImage(ref: ImageAttachmentRef): Promise<StoredImageAttachment>
+}
+
+export default AttachmentStore