[BUG]: "Configuration is currently invalid" banner doesn't name the failing keys #1246

varlock version

1.23.0 (also present on main at 8e26ef9)

Steps to reproduce

mkdir repro && cd repro
printf '# @defaultRequired=true\n# ---\nDATABASE_URL=\nAPI_TOKEN=\n' > .env.schema
echo 'console.log("started")' > child.cjs
env -i PATH="$PATH" NO_COLOR=1 npx varlock run -- node child.cjs 2>&1 | grep -m1 .

What is expected?

The first non-empty stderr line names the failing keys (names only, never values), e.g.

🚨🚨🚨  Configuration is currently invalid: DATABASE_URL, API_TOKEN  🚨🚨🚨

What is actually happening?

🚨🚨🚨  Configuration is currently invalid  🚨🚨🚨

The key names only appear in the per-item summaries printed after the banner.

System Info

Node 22, macOS. The code path (checkForConfigErrors in packages/varlock/src/cli/helpers/error-checks.ts) is platform-independent.

Any additional comments?

A lot of tooling only shows the first stderr line of a failed process: container platforms' termination reason, CI step annotations, error-tracker titles, process supervisors. With varlock run as the entrypoint, all an operator sees there is "Configuration is currently invalid", not which variable.

Key names come from the schema, not values, so adding them to the banner prints nothing sensitive. Existing tests match the banner with toContain, so they keep passing. Happy to send a PR.