Web multimodal image input and durable attachments

Web 多模态图片输入与持久附件

Before this change, the Web composer accepted only text: `InputBar` received a string draft, `ConversationController.send()` created text content, and the host forwarded that content to the agent. Users could not paste an image, inspect it before sending, submit an image-only prompt, or recover sent images from history. This is not only a composer gap. Core needs a durable image content block, providers need explicit

import type { Branded } from '@deepseek-ai/dsh-brand'

type DraftAttachmentId = Branded<'DraftAttachmentId'>

interface ChatStoreState {
  selection: object | null
  draft: string
  view: string | null
}

interface InputState {
  draft: string
  imageIds: readonly DraftAttachmentId[]
}

interface ComposerAttachment {
  kind: 'image'
  id: DraftAttachmentId
  file: File
  previewUrl: string
}

import type { Branded } from '@deepseek-ai/dsh-brand'

type AttachmentId = Branded<'AttachmentId'>

interface ImageAttachmentRef {
  attachmentId: AttachmentId
  mediaType: 'image/png' | 'image/jpeg' | 'image/webp' | 'image/gif'
  bytes: number
  width: number
  height: number
  name?: string
}

interface ImageBlock {
  type: 'image'
  attachment: ImageAttachmentRef
}

export {}

type PromptInputPart =
  | { type: 'text'; text: string }
  | {
      type: 'image'
      mediaType: 'image/png' | 'image/jpeg' | 'image/webp' | 'image/gif'
      data: string
      name?: string
    }

import type { Branded } from '@deepseek-ai/dsh-brand'

type DraftAttachmentId = Branded<'DraftAttachmentId'>

interface ChatStoreState {
  selection: object | null
  draft: string
  view: string | null
}

interface InputState {
  draft: string
  imageIds: readonly DraftAttachmentId[]
}

interface ComposerAttachment {
  kind: 'image'
  id: DraftAttachmentId
  file: File
  previewUrl: string
}

import type { Branded } from '@deepseek-ai/dsh-brand'

type AttachmentId = Branded<'AttachmentId'>

interface ImageAttachmentRef {
  attachmentId: AttachmentId
  mediaType: 'image/png' | 'image/jpeg' | 'image/webp' | 'image/gif'
  bytes: number
  width: number
  height: number
  name?: string
}

interface ImageBlock {
  type: 'image'
  attachment: ImageAttachmentRef
}

export {}

type PromptInputPart =
  | { type: 'text'; text: string }
  | {
      type: 'image'
      mediaType: 'image/png' | 'image/jpeg' | 'image/webp' | 'image/gif'
      data: string
      name?: string
    }