feat(cli): cross-flavor inline image and video display via MCP and ACP

[heavygee]

Summary

Cross-flavor inline image and video in HAPI web chat (not Cursor IDE composer):

• CLI MCP: display_image and display_video in startHappyServer; stdio bridge forwards both; buildHapiMcpBridge auto-approves both tools.
• Prompts: Shared displayImagePrompt / display_video exports for Claude, Codex, and HAPI_MCP_BRIDGE_PROMPT (Cursor, Gemini, Kimi, OpenCode first-prompt injection).
• ACP: Image content blocks → generated-image agent messages; generated media stored in CLI memory and served via hub GET /api/sessions/:id/generated-images/:imageId (images and video share this route).
• Web: GeneratedImageCard renders <img> (with tiny-image upscale + stable blob fetch) or <video controls> when mimeType is video/*.
• Tooling: hapi-display-image.mjs routes mp4/webm to display_video (absolute paths); loads hapiMcpUrl from per-session GET.

Test plan

• bun typecheck
• CLI: generatedImages.test.ts, buildHapiMcpBridge.test.ts, codexMcpConfig.test.ts, AcpMessageHandler.test.ts, messageConverter.test.ts
• Web: generatedInlineMedia.test.ts
• Manual: display_image PNG and display_video MP4 on Cursor session with hapiMcpUrl; inline cards in HAPI web

Issues

Closes #956

[github-actions]

Findings

• [Major] ACP inline media can be emitted before preceding assistant text. The new image branch flushes reasoning but leaves bufferedText open, while emitGeneratedImageFromAcpContent() emits asynchronously. For a normal ACP sequence like text chunk -> image block -> turn drain, the generated-image message can reach the web UI before the text that came first in the stream. Evidence: cli/src/agent/backends/acp/AcpMessageHandler.ts:559.

Questions

• None.

Summary

• Review mode: initial
• One ordering regression found in the latest diff. Residual risk: media fetch/cache behavior was reviewed statically only.

Testing

• Not run (automation). Suggested coverage: ACP handler test that sends a text agentMessageChunk, then an image agentMessageChunk, then drains, and asserts text precedes generated_image.

[github-actions]

[Major] Flush buffered assistant text before emitting ACP media. Text chunks in this handler are buffered until flushText()/drainBuffers(), but this new image branch only flushes reasoning before kicking off async media registration. For a stream that sends text, then an image block, then ends the turn, the image can be delivered before the preceding text and the chat order is wrong.

Suggested fix:

if (isObject(content) && content.type === 'image') {
    this.flushReasoning();
    this.flushText();
    void this.emitGeneratedImageFromAcpContent(content);
    return;
}