fix mysql introspection json columns

[aiprojectchiwa]

Summary

Fix MySQL/MariaDB introspection in Prisma Studio when the introspection query returns aggregated columns as a JSON string instead of an array.

This prevents Studio from crashing with errors like:

• a.sort is not a function
• columns.sort is not a function

Root cause

Some MySQL-compatible backends (notably MariaDB variants) can return the json_arrayagg(...) result as a string payload. The adapter assumed columns was always already an array and called .sort() directly.

Fix

• Normalize columns before sorting
• Parse JSON string payloads when needed
• Keep the existing behavior unchanged for proper array results
• Add a regression test covering the string-returning case

Verification

Validated on Node 24.13.0 with:

• pnpm typecheck
• pnpm exec eslint data/mysql-core/adapter.ts data/mysql-core/introspection-hardening.test.ts
• pnpm test:data
• pnpm build
• pnpm check:exports