docs: finish scrubbing tokenizer references after estimator-cluster removal

Follow-up to 0ee17632c7/1871bb5b81 (review round 2):
- supportedImageFormats.ts header and getSupportedImageFormatsString doc
  no longer describe a tokenizer decode/metadata-extraction stage; the
  list is now documented as the vision-input acceptance list, with token
  accounting noted as the flat DEFAULT_IMAGE_TOKEN_ESTIMATE.
- web-shell-image-drag-and-drop.md's BMP rationale no longer claims
  ImageTokenizer parses BMP dimensions; dated sync note added stating
  BMP support rests on SUPPORTED_IMAGE_MIME_TYPES plus converter
  passthrough since PR #9676.

docs/design/web-shell/web-shell-image-drag-and-drop.md

@@ -502,9 +502,14 @@ oversized placeholder。它们验证既有服务端契约；Web Shell helper 测
 候选顺序和 encoded-data 剩余预算。
 
 BMP 以 `image/bmp` 进入缩略图 data URL 和 daemon image block。Core 的
-`SUPPORTED_IMAGE_MIME_TYPES` 明确包含 `image/bmp`，`ImageTokenizer` 解析 BMP 尺寸，
-OpenAI converter 把启用 image modality 的 `inlineData` 原样构造成
-`data:image/bmp;base64,...`；Gemini 路径保留相同 `inlineData`。因此 V1 不在浏览器转码。
+`SUPPORTED_IMAGE_MIME_TYPES` 明确包含 `image/bmp`，OpenAI converter 把启用 image modality 的
+`inlineData` 原样构造成 `data:image/bmp;base64,...`；Gemini 路径保留相同 `inlineData`。
+因此 V1 不在浏览器转码。
+
+> **2026-08-24 同步注记（PR #9676）**：request-tokenizer 估计器簇（含 `ImageTokenizer`
+> 及其 BMP 尺寸解析）已作为孤儿代码删除。BMP 支持现在仅依赖 `SUPPORTED_IMAGE_MIME_TYPES`
+> 接受清单与 converter 透传；token 计数使用 `compactionInputSlimming.ts` 中的固定
+> `DEFAULT_IMAGE_TOKEN_ESTIMATE`。下文对 BMP 路径的 E2E/人工验收要求不变。
 浏览器若不能解码缩略图，不影响附件数据传输，但 E2E 必须覆盖 Chromium 解码，
 Firefox/Linux 必须完成人工验收。
 

packages/core/src/utils/request-tokenizer/supportedImageFormats.ts

@@ -5,11 +5,15 @@
  */
 
 /**
- * Image MIME types the image tokenizer can decode for metadata extraction.
- * This is a capability list, not an acceptance contract: the file-read path
- * only forwards a narrower set to model endpoints (see
- * PROVIDER_SAFE_IMAGE_MIME_TYPES in fileUtils.ts and #9291), so some types
- * here are omitted from requests before they ever reach the tokenizer.
+ * Image MIME types accepted for vision input (attachment/thumbnail paths).
+ * This is an acceptance list for inputs, not a decode-capability list:
+ * token accounting uses the flat DEFAULT_IMAGE_TOKEN_ESTIMATE in
+ * compactionInputSlimming.ts — the former request-tokenizer estimator
+ * cluster, including ImageTokenizer and its dimension parsing, was removed
+ * as orphaned in PR #9676. The file-read path forwards only the narrower
+ * PIPELINE_IMAGE_MIME_TYPES subset to model endpoints (see
+ * PROVIDER_SAFE_IMAGE_MIME_TYPES in fileUtils.ts and #9291); anything else
+ * is omitted from requests with an in-band notice.
  */
 export const SUPPORTED_IMAGE_MIME_TYPES = [
   'image/bmp',
@@ -58,7 +62,7 @@ export function isSupportedImageMimeType(
 
 /**
  * Get a human-readable list of image formats the pipeline forwards to the
- * model (not the tokenizer's wider decode capability).
+ * model (the narrower pipeline subset, not the full acceptance list above).
  * @returns Comma-separated string of forwarded formats
  */
 export function getSupportedImageFormatsString(): string {