feat: pending-finish proposals and QQ image input

Proposal semantics: worker results no longer distinguish success/fail;
only an explicit finish settles a pending proposal. Pending owner input
follows up by resuming the original worker session. Dirty pending blocks
start_next globally; clean pending only blocks its owner.

QQ adapter now downloads image attachments and passes them as ACP image
content blocks; video/file attachments degrade to link text.

test/acp-client.test.ts

@@ -1,5 +1,8 @@
 import assert from "node:assert/strict";
 import { spawn } from "node:child_process";
+import crypto from "node:crypto";
+import fs from "node:fs";
+import os from "node:os";
 import path from "node:path";
 import test from "node:test";
 import type { RequestPermissionRequest } from "@agentclientprotocol/sdk";
@@ -51,3 +54,37 @@ test("reports activity for every update from the active session", async () => {
     child.kill("SIGTERM");
   }
 });
+
+test("prompt sends text and image content blocks and records the image capability", async () => {
+  const logFile = path.join(os.tmpdir(), `gori-acp-client-${crypto.randomUUID()}.log`);
+  const fixture = path.resolve("test/fixtures/fake-acp-agent.mjs");
+  const child = spawn(process.execPath, [fixture], {
+    stdio: ["pipe", "pipe", "pipe"],
+    env: { ...process.env, FAKE_ACP_LOG: logFile }
+  });
+  const client = new AcpClient(child, {
+    initializeTimeoutMs: 1_000,
+    policy: { mode: "deny", allowedTools: [], allowedCommandPatterns: [] }
+  });
+  try {
+    await client.initialize();
+    assert.equal(client.supportsImageInput(), true);
+    await client.newSession(path.resolve("."));
+    const image = Buffer.from("fake-png").toString("base64");
+    const reply = await client.prompt([
+      { type: "image", data: image, mimeType: "image/png" },
+      { type: "text", text: "hello blocks" }
+    ]);
+    assert.match(reply, /^reply:.+:hello blocks$/);
+    const prompts = fs.readFileSync(logFile, "utf8").trim().split("\n").filter(Boolean)
+      .map((line) => JSON.parse(line) as { method: string; text?: string; images?: number })
+      .filter((entry) => entry.method === "session/prompt");
+    assert.equal(prompts.length, 1);
+    assert.equal(prompts[0]!.text, "hello blocks");
+    assert.equal(prompts[0]!.images, 1);
+  } finally {
+    client.close();
+    child.kill("SIGTERM");
+    await fs.promises.rm(logFile, { force: true });
+  }
+});