fix(qwen): remove dangling QWEN.md context reference

[KDB-Wind]

Summary

Remove the dangling contextFileName: "QWEN.md" declaration from
qwen-extension.json because the referenced file does not exist in the
repository and is not included in the published npm package.

Update the manifest test to require the field to remain absent. No replacement
QWEN.md is introduced, so this change does not add extension-wide context or
alter the canonical root skills/ behavior.

Why

• Issue/Story: No issue; justified maintenance of the shipped Qwen Code
  extension manifest.
• User or maintainer outcome: Qwen Code no longer presents an install-time
  promise to append extension context from a file the extension cannot provide.

Qwen Code 0.21.1 was verified on Windows through both registration paths with
isolated QWEN_HOME directories:

• qwen extensions link <local-path>
• qwen extensions install <git-repository-url>

Current upstream displayed the same dangling QWEN.md context message through
both paths. The fixed branch omitted the message while retaining the
better-harness Skill. A fixed Git-ref install was completed inside the
isolated home and confirmed with qwen extensions list; no chat or LLM call
was made.

Traceability and Scope

• Spec/ADR, if applicable:
  docs/specs/2026-07-29-qwen-extension-context-file.md
• Acceptance criteria addressed:
  • AC-1: qwen-extension.json no longer declares contextFileName; all
    remaining manifest fields are unchanged.
  • AC-2: test/plugin-manifests.test.mjs requires
    qwen.contextFileName === undefined.
  • AC-3: The focused plugin-manifest tests pass 3/3.
  • AC-4: Package verification passes and keeps the packaged Qwen manifest
    version-aligned with package.json.
  • AC-5: Qwen Code 0.21.1 link and Git-ref install omit the dangling context
    promise, retain Skill discovery, and can be listed from an isolated home.
• Canonical owners changed:
  • qwen-extension.json
  • test/plugin-manifests.test.mjs
  • docs/specs/2026-07-29-qwen-extension-context-file.md
• Explicit non-goals:
  • No new extension-owned QWEN.md.
  • No change to the workspace-level QWEN.md inventory.
  • No change to the Qwen session analyzer or configured-asset provider.
  • No change to other host manifests.
  • No new Qwen capability or installation command.

Change Type

• Feature
• Bug fix
• Tests only
• Documentation/community
• Refactor with no intended behavior change
• Dependency, packaging, or infrastructure

Test and Review Evidence

Check	Result
node --test test/plugin-manifests.test.mjs test/doc-link-graph.test.mjs	9/9 pass
npm run pack:verify	Pass: npm 319 entries, runtime ZIP 343 entries
git diff --check origin/main	Pass
Qwen 0.21.1 isolated link/install/list	Pass; no LLM call
Full npm test	881 total: 876 pass, 2 baseline failures, 3 skipped
Full npm test on unmodified current upstream	Same 876/2/3 result

Manual evidence: the repository contains no root QWEN.md, and the
package.json files list does not ship one. The staged patch was also
compared with the reviewed source patch before the final commit was created.

The two full-suite failures reproduce on unmodified current upstream:

• one instruction-ledger test detects an environment-provided ancestor
  CLAUDE.md;
• one Windows review-trigger fixture expects Git inspection to fail, but its
  simulated command exits zero in this environment.

Focused affected-area tests and package verification pass. Clean GitHub CI
remains the authoritative full-suite result.

Risk and Recovery

• Compatibility and cross-platform impact: The manifest change is
  platform-neutral JSON. It removes an undeliverable context reference and
  leaves Skill discovery unchanged.
• Package, plugin, schema, or generated-file impact: The published
  qwen-extension.json changes by one optional field. Package verification
  passes; no schema or generated file changes.
• Rollback or recovery path: Revert the single commit to restore the field.
• Residual risk or unverified boundary: Maintainers may prefer to ship a real
  extension-owned QWEN.md instead. That would be a product decision requiring
  the file, package inclusion, context content review, and an existence test.
• Changelog boundary: No release entry is added because this removes a
  declaration for behavior that was never deliverable; it introduces no new
  capability.

AI Involvement

• Level: Assisted
• Human review and validation: AI assisted with drafting and reviewing the
  patch, spec, and validation workflow. The contributor made and reviewed the
  remove-versus-add product decision, inspected the final diff and acceptance
  criteria, and checked the recorded validation evidence. The focused tests,
  doc-link checks, package verification, and diff checks were rerun after the
  final commit was rebuilt.

Checklist

• I followed AGENTS.md, CONTRIBUTING.md, and the relevant canonical-owner guidance.
• The change is focused and does not include unrelated local or generated state.
• Tests and documentation match the behavior actually delivered.
• Markdown links were checked when documentation moved or changed.
• Cross-platform behavior was considered for Windows, macOS, and Linux.
• Package/runtime verification was run when shipped files or dependencies changed.
• User-facing or compatibility changes are recorded in CHANGELOG.md, or the no-entry rationale is documented above.
• I have the right to contribute this work under the repository's MIT License.