Determinism is now enforced, not assumed

A conformance harness guards a core invariant: one indexer and N indexers folding the same ledger range must produce byte-identical gold.

• Reference-run-twice byte-identity plus N-way union equality, asserted against real database containers.
• Deterministic reducers: deltas sorted before emit; no floats, clocks, or randomness in the core.
• Schema-freeze guards on bronze and gold wired into the test suite, so an accidental schema change fails loudly instead of shipping.