[Phase 0] Implement automated dynamic profiling and drift checks #340
Description
Type: feature
Suggested labels: phase-0, data-quality, automation
Add automated profiling and deviation checks so quality assessment scales with source count.
Acceptance criteria:
- Profiling baselines are computed per source/model.
- CI fails on statistically significant drift for key metrics (null ratio, cardinality, row deltas, distribution changes).
- Alert output clearly identifies source/model/field that deviated.
Dependencies: #5