feat(engine): add Qwen Code to the external agent registry (#7293)

Qwen Code starts in ACP mode with `qwen --acp`, the flag that replaced
`--experimental-acp` in 0.6.1, so that is the version floor. Sign-in is
`/auth` inside an interactive session (`qwen auth` was removed), so the
row has no login command.

crates/engine/src/fleet/agents.rs

@@ -187,6 +187,19 @@ pub const AGENTS: &[ExternalAgent] = &[
         adapter_binary: None,
         adapter_cli_env: None,
     },
+    ExternalAgent {
+        id: "qwen-code",
+        name: "Qwen Code",
+        binary: "qwen",
+        acp_args: Some(&["--acp"]),
+        website: "https://github.com/QwenLM/qwen-code",
+        min_version: Some("0.6.1"),
+        upgrade: Some("npm i -g @qwen-code/qwen-code@latest"),
+        login: None,
+        adapter: None,
+        adapter_binary: None,
+        adapter_cli_env: None,
+    },
 ];
 
 const FIXTURE_AGENT: ExternalAgent = ExternalAgent {

docs/RUNTIME_API.md

@@ -3270,7 +3270,7 @@ refuses OpenAI Codex. An Engine without this route answers `404`.
 
 Reports which external agent CLIs this computer already has, without starting a
 session. It covers Claude, Codex, DeepSeek Harness, Antigravity (`agy acp`),
-OpenCode, Kimi Code, Mistral Vibe, Qoder, CodeBuddy and Grok. `state` is `installed` or `not_installed`; a binary is
+OpenCode, Kimi Code, Mistral Vibe, Qoder, CodeBuddy, Grok and Qwen Code. `state` is `installed` or `not_installed`; a binary is
 looked up on `PATH` (absolute entries only; on Windows the spawnable PATHEXT suffixes `.com/.exe/.bat/.cmd` and `%APPDATA%\npm`) and in the usual per-user bin directories. For an installed
 agent the route runs `--version` and, where the CLI speaks Agent Client Protocol
 itself, one `initialize` request on stdin, concurrently. `acp` is `native` when