feat(nextjs): point missing-key errors at the Clerk CLI

[djgould]

Description

Part 2 of the keyless→CLI stack, stacked on #9484. Extends the CLI-first error messaging to production:

• @clerk/shared: default missing publishableKey/secretKey messages now recommend npx clerk@latest init.
• @clerk/nextjs: clerkMiddleware() with missing keys outside development now throws a deploy-oriented error recommending npx clerk@latest deploy, with npx clerk@latest env pull --instance prod as the already-deployed fallback (code=missing_env_keys_production).

Dev keeps the keyless init error from #9484; the shared init default covers non-Next SDKs.

Supersedes #9481 (same content, restacked fresh off main).

Checklist

• pnpm test runs as expected.
• pnpm build runs as expected.
• (If applicable) JSDoc comments have been added or updated for any package exports
• (If applicable) Documentation has been updated

Type of change

• 🌟 New feature

🤖 Generated with Claude Code

[vercel]

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Project	Deployment	Actions	Updated (UTC)
clerk-js-sandbox	Ready	Preview	Aug 18, 2026 6:20pm
swingset	Ready	Preview	Aug 18, 2026 6:20pm

[changeset-bot]

🦋 Changeset detected

Latest commit: 5dba032

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 23 packages

Name	Type
@clerk/shared	Patch
@clerk/astro	Patch
@clerk/backend	Patch
@clerk/chrome-extension	Patch
@clerk/clerk-js	Patch
@clerk/electron	Patch
@clerk/expo-passkeys	Patch
@clerk/expo	Patch
@clerk/express	Patch
@clerk/fastify	Patch
@clerk/headless	Patch
@clerk/hono	Patch
@clerk/localizations	Patch
@clerk/msw	Patch
@clerk/nextjs	Patch
@clerk/nuxt	Patch
@clerk/react-router	Patch
@clerk/react	Patch
@clerk/tanstack-react-start	Patch
@clerk/testing	Patch
@clerk/ui	Patch
@clerk/vue	Patch
@clerk/swingset	Patch

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