docs: document Node 26 fetch failed workaround

[debpramanik]

Summary

• Document a Node.js v26-specific cause for [API Error: Connection error. (cause: fetch failed)]
• Add Node.js v22.22.3 LTS as the immediate workaround
• Clarify that if curl/direct Node requests work, the base URL, model IDs, and API key may already be correct

Problem

Qwen Code can show [API Error: Connection error. (cause: fetch failed)] for every API call even though curl and direct node requests reach the endpoint fine.

Root Cause

Node.js v26.0.0 can be incompatible with Qwen Code 0.15.11's HTTP client path using undici/OpenAI SDK, causing the SDK request pipeline to fail before the endpoint is reached.

Fix / Workaround

Downgrade Node.js from v26.0.0 to v22.22.3 LTS and retry with the same Qwen Code config.

Validation

Docs-only change. The workaround was validated by switching Node.js v26.0.0 to v22.22.3 LTS while keeping the same base URL, model IDs, and API key.

[wenshao]

[Suggestion] The hardcoded version pins "Qwen Code 0.15.11" and "Node.js v22.22.3 LTS" will become stale quickly. 0.15.11 is the only Qwen Code version pin anywhere in docs/; once 0.16+ ships (or once Node v26 itself becomes LTS), readers won't know whether the workaround still applies. .nvmrc already targets 22 (no patch) and engines says >=22.0.0, so v22.22.3 is unnecessary precision.

Consider version-agnostic phrasing plus a tracking link so future maintainers can tell whether the root cause is resolved:

Suggested change

	- **Cause:** Node.js v26 can be incompatible with the HTTP client path used by Qwen Code 0.15.11. In this case, Qwen Code may fail before it opens a network connection even when the same endpoint, model, and API key work with `curl` or a direct `node` `fetch()` request.
	- **Error: `[API Error: Connection error. (cause: fetch failed)]` on every API call with Node.js v26.**
	- **Cause:** Node.js v26 can be incompatible with the HTTP client path used by Qwen Code (known to affect versions up to 0.15.11). In this case, Qwen Code may fail before it opens a network connection even when the same endpoint, model, and API key work with `curl` or a direct `node` `fetch()` request.
	- **Solution:** Use a supported Node.js LTS release (v22.x). For example:
	```bash
	nvm install 22
	nvm use 22
	qwen -p "hi"
	```
	- **How to verify:** If the request works after switching Node.js versions, your base URL, model IDs, and API key were likely already correct; the Node.js runtime version was the blocker.

Note: Node.js v26 satisfies the >=22.0.0 engine requirement, so npm install succeeds without warning — the incompatibility only manifests at runtime. Consider mentioning this so users on v26 aren't surprised by a clean install followed by a runtime failure.

— qwen-latest-series-invite-beta-v28 via Qwen Code /review

[wenshao]

[Suggestion] Unrelated drive-by change: this line swaps → (unicode) for -> (ASCII), but the PR title/body only describe the Node.js v26 entry. The unicode → is the established convention in 20+ locations across docs/users/ (e.g. CLI → env → settings → defaults, Run qwen → /auth, Continue with Quickstart (5 mins) →). After this change, line 14 becomes the sole outlier in instructional prose.

Suggested: revert to → here, or — if the intent is to standardize on ASCII arrows — split that into a separate PR with a matching scope description.

Suggested change

	- **Solution:** Switch to a different authentication method. Run `qwen` -> `/auth` and choose one of:
	- **Solution:** Switch to a different authentication method. Run `qwen` → `/auth` and choose one of:

— qwen-latest-series-invite-beta-v28 via Qwen Code /review