nextdoctor fix

Applies the safe, auto-fixable findings from diagnose — adds onDemandEntries tuning, removes an accidentally-disabled turbopackMemoryEviction: false, etc.

Safety

• Always backs up your existing config first (next.config.js.nextdoctor-backup-<timestamp>)
• Shows you exactly what it's about to change before writing anything
• Refuses to run if the working tree (inside a git repo) has uncommitted changes, so the diff it makes stays easy to review in isolation — pass --allow-dirty to override
• Pass -y to skip the confirmation prompt (e.g. in a setup script)

How the config insertion works

Conservative, regex-based text patching rather than a full AST rewrite, specifically so diffs stay obvious and reviewable. It handles both plain const nextConfig = { configs and typed next.config.ts written as const nextConfig: NextConfig = { (the pattern create-next-appitself generates). Unusual shapes it doesn't recognize fall back to appending a block at the end of the file — always review the diff either way.