fix(desktop): provide WorkHub enablement in dock tests

[Astro-Han]

Summary

Restore Desktop CI compilation by mounting WorkHubEnablementProvider in the WorkHub dock test fixture instead of passing the retired enabled prop.

Refs #5936 and #5938. The dock now reads its switch from the existing provider, but the newly merged fixture still used the old API. This breaks build:main on main and downstream PRs with TS2769 at workhub-dock.test.ts:99 (first failing main run).

Only the test composition changes; production behavior, protocol and migration requirements are unchanged. Existing backdrop handoff assertions remain intact.

Verification

• GitHub CI passed on the PR merge result: run 38048540622.

• Reproduced the original TS2769 with npm run build on current main after installing locked dependencies and refreshing local incremental caches.

• npm --workspace @maka/desktop run build — passed.

• node --test --test-concurrency=4 dist/main/__tests__/workhub-dock.test.js dist/main/__tests__/workhub-enablement.test.js from apps/desktop — 16 passed.

• npm --workspace @maka/desktop run typecheck — passed.

• npm run format and npm run lint — passed, no fixes needed.

• Full-repository tests and local Electron E2E were not run; CI covers its selected surfaces.

AI use

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: Maka (gpt-6.1-sol) diagnosed the failures, updated the test fixture, and ran verification.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No