feat: add model-aware DSH image input

DeepSeek Harness previously treated every selected model as text-only. It now carries the model profile's image capability through Main, the Utility Host, ACP, and Pi-AI, rejects unsupported images before model invocation, and validates supported JPEG/PNG data in a bounded process-local attachment store.

The Composer keeps universal controls on its first row, places OpenCode and Continue controls on a dedicated responsive row, and anchors context compaction without shifting the footer. Runtime supervision ownership for future Subagents and Jobs is documented for the right sidebar.

Release note: DeepSeek Harness 现可按所选模型连接的能力安全接收 JPEG/PNG 图片；Composer 同时将 Runtime 专属选择器移到独立一行，并固定上下文压缩入口。

package-lock.json

@@ -35,6 +35,7 @@
         "@deepseek-ai/dsh-tools": "0.1.0-rc.6",
         "@deepseek-ai/dsh-user-approval": "0.1.0-rc.6",
         "@modelcontextprotocol/sdk": "^1.30.0",
+        "@napi-rs/canvas": "1.0.3",
         "@opencode-ai/sdk": "^1.18.9",
         "@wecom/aibot-node-sdk": "^1.0.6",
         "cross-spawn": "^7.0.6",