Idempotent upsert keyed on pack_id; slot rates and card weights are
wiped per pack and reinserted. String slot/tier in the seed translate
to enum at import time.
Tests:
- Imports_config_slot_rates_and_card_weights
- Is_idempotent_on_rerun
Fixtures live under SVSim.Bootstrap/Data/test-fixtures/seeds/ and overlay
the production seeds via the existing csproj rule (test-fixture file
beats production file at same Link path).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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