Resolve merge conflicts: add brain/sync-check scripts, dual API key support, and Gemini direct streaming to beauty-assistant

[Copilot]

Merges diverged changes from copilot/fix-merge-conflicts into main across four files. The feature branch added new operational scripts, npm shortcuts, and a significant refactor of the beauty-assistant edge function; main had moved ahead with a newer jsdom version. Conflicts resolved by taking the best of both.

README.md

• Added SNC (sync:check) documentation section and full Available scripts table

package.json

• Added health, brain, sync:check npm scripts
• Kept jsdom@^28.1.0 from main (dropped ^20.0.3 from feature branch)

New scripts

• scripts/brain-check.js — HTTP GET probe against the beauty-assistant edge function
• scripts/sync-check.js — parallel probe of frontend /health + beauty-assistant; exits non-zero on any failure

supabase/functions/beauty-assistant/index.ts

• Added JSDoc header and declare const Deno ambient declaration (fixes TS compiler errors on Deno URL imports; paired with // @ts-expect-error)
• Replaced all Deno.env.get(...)! non-null assertions with ?? "" / guarded patterns
• Dual API key support in website chat path: GEMINI_API_KEY ?? LOVABLE_API_KEY
• Gemini direct streaming (streamGenerateContent SSE) added as a second path when LOVABLE_API_KEY is absent:

if (useLovable) {
  // existing Lovable gateway path (stream: true)
} else {
  // new: Gemini streamGenerateContent → forward as SSE
  const geminiRes = await fetch(
    `https://generativelanguage.googleapis.com/v1beta/models/${model}:streamGenerateContent?key=${apiKey}&alt=sse`,
    ...
  );
}

• Added null-body guards (if (!response.body) { controller.close(); return; }) before all getReader() calls

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