Enforce notebook determinism

Enforce notebook reproducibility and eliminate non-determinism

When enforcing notebook reproducibility and eliminating non-deterministic patterns in data pipelines

• · Notebook cells with datetime, uuid, random calls, query results

• · Cleaned cells, determinism sweep report (errors: 0)

• · check_notebook_determinism_contracts.sh

• · Notebook cells must pass determinism sweep in strict mode

• · datetime.now() or datetime.utcnow() left in cell
• · uuid.uuid4() generating random IDs
• · pandas.sample() without random_state
• · Query results not ordered before limit (order-by missing)
• · Weak determinism mode used as workaround
• · Demo semantics changed while fixing determinism

• · Hard patterns list (datetime.now, datetime.utcnow, date.today, time.time, uuid.uuid4, pandas.sample)
• · Strict mode enforcement (no exceptions)
• · Sweep script with clear error reporting