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。

src/main/agent/create-runtime.ts

@@ -171,6 +171,7 @@ export function createAgentRuntime(
       defaultWorkspace: workspace,
       baseUrl: profile.baseUrl,
       model: profile.modelName,
+      supportsImageInput: profile.supportsImageInput === true,
       launch: capabilities.deepseekHarnessLauncher,
       credentialRefs: {
         GOODBUDDY_HARNESS_MODEL_API_KEY: profile.apiKey