test(integration): give the ACP parity rig a scratch runtime directory (#16224)

* test(integration): give the ACP parity rig a scratch runtime directory

TestRig points QWEN_RUNTIME_DIR at `<testDir>/.qwen-home`, and the parity
rig forwarded only QWEN_HOME to both ACP surfaces. Session runtime state
(`tmp/<hash>`, token usage) therefore landed inside the workspace, so the
folder-structure snapshot embedded in each request listed
`.qwen-home/tmp/<hash>` for the surface that inherited the rig's runtime and
not for the other: `expect(shared.requests).toEqual(current.requests)` then
failed whenever that ordering broke, and the retry went green (run
41668631944, first attempt failing three parity cases).

Point QWEN_RUNTIME_DIR at the same scratch home as QWEN_HOME so neither
surface writes into the workspace.

Verified with the fixed bundle: 24/24 parity cases pass. With KEEP_OUTPUT,
the test directory now holds `.qwen-home/settings.json` and
`trustedFolders.json` only, where origin/main additionally creates
`.qwen-home/tmp/<hash>` for the same case.

* test(integration): keep the ACP parity scratch runtime under KEEP_OUTPUT

Checkpoint for review suggestions R1-1/R1-2 on #16224. The parity rig now
keeps its scratch QWEN_HOME when KEEP_OUTPUT is set, matching
TestRig.cleanup()'s truthiness check, and pins the absence of the default
`<testDir>/.qwen-home/tmp` runtime directory directly instead of relying on
the request-snapshot diff.

Not verified locally: `npm run bundle` cannot resolve the generated
web-templates sources in this worktree, so the parity case was not executed.

Co-authored-by: Qwen-Coder <[email protected]>
Patrol-Run: qwen-pr-closeout/jmw14zt15bk

---------

Co-authored-by: Qwen-Coder <[email protected]>

integration-tests/cli/acp-agent-loop-parity.test.ts

@@ -302,6 +302,11 @@ const allowOnce = () => ({
         NO_PROXY: noProxy,
         no_proxy: noProxy,
         QWEN_HOME: qwenHome,
+        // TestRig keeps QWEN_RUNTIME_DIR inside the workspace; leaving it
+        // there makes the session runtime write `tmp/<hash>` into the test
+        // directory, which then differs between the two surfaces' request
+        // snapshots. Give both surfaces the same scratch runtime.
+        QWEN_RUNTIME_DIR: qwenHome,
       };
       delete env['QWEN_CODE_ENABLE_UNIFIED_AGENT_LOOP'];
       if (shared) env['QWEN_CODE_ENABLE_UNIFIED_AGENT_LOOP'] = '1';
@@ -496,8 +501,16 @@ const allowOnce = () => ({
           if (agent.exitCode !== null || agent.signalCode) resolve(undefined);
           else agent.once('exit', resolve);
         });
-        await removeScratchDir(qwenHome);
+        // Keep the runtime state for post-mortem whenever TestRig.cleanup()
+        // keeps the test directory, which it decides by truthiness.
+        if (!process.env['KEEP_OUTPUT']) {
+          await removeScratchDir(qwenHome);
+        }
       }
+      // The scratch runtime is what keeps the session runtime's `tmp/<hash>`
+      // out of the workspace, so pin its absence rather than relying on the
+      // snapshot diff, which only trips on the losing side of a race.
+      expect(existsSync(join(dir, '.qwen-home', 'tmp'))).toBe(false);
       return {
         requests: modelRequests(server, dir),
         dateReminders: streamingMessages(server).filter((messages) =>