fix(contentful-nextjs): draftMode() and page params are async since Next.js 15

[milescontentful]

Summary

The Draft Mode reference example (skills/contentful-nextjs/references/preview-and-draft-mode.md) still showed the pre-Next.js-15 synchronous form:

export default async function Page({ params }: { params: { slug: string } }) {
  const { isEnabled } = draftMode();
  const entry = await getEntryById(params.slug, isEnabled);

draftMode() has been async since v15.0.0-RC, and page params became a Promise in the same release. Copying this example as-is on a current Next.js project produces a type error (or triggers the deprecated synchronous-access warning, which Next.js says will stop working in a future version).

Fixed to await both, matching the current official docs example.

Test plan

• Confirmed the fix against the live Next.js docs (draftMode API reference, version 16.2.12, "Good to know" section: "draftMode is an asynchronous function that returns a promise... In version 14 and earlier, draftMode was a synchronous function... this behavior will be deprecated in the future").
• python3 local-skills/skills/skill-authoring/scripts/quick_validate.py skills --all — 7/7 skills pass, including contentful-nextjs.
• Scoped to this one file — no other changes.

🤖 Generated with Claude Code

[François (Lp-Francois)]

Good catch, thanks!