[evidence] spark setup does not write SPARK_BUILDER_REPO to spawner-ui env - causes creator missions to fail

[Acone8]

Before: spawner-ui.env is missing SPARK_BUILDER_REPO so /creator plan fails with "Builder repo not found: /Users/cyprian/.spark/modules/spawner-ui/spark-intelligence-builder".

After: Manually adding SPARK_BUILDER_REPO to spawner-ui.env fixes the issue. /creator plan now stages successfully.

Repro steps:

1. Run spark setup normally
2. Check ~/.spark/config/modules/spawner-ui.env - SPARK_BUILDER_REPO is missing
3. Compare with ~/.spark/config/modules/spark-telegram-bot.env which correctly has SPARK_BUILDER_REPO set
4. Send /creator plan in Telegram and observe the wrong path error