Drop the `image` content block until a path can honor it
移除 `image` 内容块，直到有路径能真正处理它
`ImageBlock` (`packages/llm/llm/src/types.ts`) had no production producer, and every consumer on every path DROPPED it: the DeepSeek adapter's serializer skipped image blocks (a documented MVP limitation), the pi-ai converter skipped them as unrepresentable, and the compaction estimator charged a flat token constant and rendered `[image]`. ACP independently rejected image prompt content. An `ImageBlock` constructed t
English
Problem
ImageBlock (packages/llm/llm/src/types.ts) had no production producer, and every consumer on every path DROPPED it: the DeepSeek adapter's serializer skipped image blocks (a documented MVP limitation), the pi-ai converter skipped them as unrepresentable, and the compaction estimator charged a flat token constant and rendered [image]. ACP independently rejected image prompt content. An ImageBlock constructed then would silently vanish from the provider wire — the vocabulary advertised a capability no path honored, which is the silent-data-loss shape AGENTS.md's defensive patterns warn against. The only constructors anywhere were tests pinning the skip/drop/estimate branches.
Decision
Remove ImageBlock, its map entry, and image-specific branches from adapters and compaction. Update the owning vocabulary docs and generated references in the same change. Unknown extension blocks still exercise default branches, and ACP continues to reject inbound image prompt content independently of the harness vocabulary.
Alternatives considered
Why not keep it?
ContentBlockMap can reintroduce images when adapters and compaction support them. ACP may remain a text-only automation protocol. Keeping a core type whose only implementation is rejection would advertise an unusable surface; absence gives producers an immediate compile-time failure instead.
The documented fallback, should the slot ever return ahead of a full feature: keep ImageBlock but replace every silent skip with a loud rejection, and document that policy in the vocabulary — the silent drop was the one state with no defender.
Verification
No harness ImageBlock is constructed outside Agent Note records. ACP's independent inbound-image rejection remains tested, while adapter, codec, and compaction default branches are covered with plugin-defined block types.
Consequences
Re-adding a core vocabulary type later touches several packages at once — but that coordinated change is the shape a real multimodal feature needs anyway (adapter mapping and compaction pricing), and none of it existed to preserve.
中文
问题
ImageBlock（packages/llm/llm/src/types.ts）没有任何生产环境的生产者，而每条路径上的每个消费方都将其丢弃：DeepSeek 适配器的序列化器跳过 image 块（这是文档中注明的 MVP 限制）；pi-ai 转换器因无法表示而跳过；压缩（compaction）估算器为其按固定常量计入 token 用量，并将其渲染为 [image]。ACP（Agent Client Protocol）独立地拒绝图像提示词内容。此时构造的 ImageBlock 会从提供方协议格式（wire format）中静默消失——词汇宣告了一种没有任何路径兑现的能力，这正是 AGENTS.md 防御性模式所警告的静默数据丢失形态。唯一的构造调用出现在测试中，用于覆盖 skip/drop/estimate 分支。
决策
移除 ImageBlock、其 map 条目，以及适配器和压缩中的 image 专用分支。在同一个变更中更新所属的词汇文档与生成的参考文档。未知扩展块仍然覆盖默认分支，ACP 继续独立于 harness 词汇拒绝入站的图像提示词内容。
曾考虑的替代方案
为什么不保留？
当适配器和压缩支持 image 时，ContentBlockMap 可以重新引入 image 内容块。ACP 可以继续作为纯文本的自动化协议。保留一个唯一实现就是拒绝的核心类型，等于宣告一个不可用的对外服务接口；移除后，生产者会立即得到编译期错误。
文档化的回退方案（以备该词汇项在完整功能就绪之前回归）：保留 ImageBlock，但将所有静默跳过替换为显式拒绝，并在词汇文档中记录该策略——静默丢弃是唯一无人主张保留的状态。
验证
除 Agent Note 之外，没有任何地方构造 harness ImageBlock。ACP 独立的入站图像拒绝路径仍有测试；适配器、codec 和压缩的默认分支则使用插件定义的块类型覆盖。
后果
日后重新添加核心词汇类型需要同时改动多个包——但这种协调变更本就是真正的多模态功能所需的形态（适配器映射与压缩定价），而当前并不存在需要保留的实现。