Trace immutable data revisions and validate frozen paired results

[PureSaber]

Summary

Data corrections now have an immutable downstream impact path over the existing ArtifactStore. RevisionRegistry records pinned derivation descriptors, follows both existing snapshot dependency edges and registered producer inputs, and computes the complete transitive affected set independently of traversal order.

Frozen paired comparison verifies exact input substitution, code hashes and controls before reporting JSON and decimal changes. It preserves both historical results, rejects changed code/control confounding, and exposes a read-only CLI. Reachability is explicitly not causal proof; actual producer execution verification is supplied by the dependent portfolio workflow.

Verification

• Full Windows/Python 3.12 suite: 1023 passed, 8 skipped; required pure branch gates passed (all tracked source branches 80.67%).
• Ruff check and format passed.
• New controls cover corruption, self/cyclic dependencies, snapshot member lineage, diamond closure order, frozen-pair confounding, exact numerical deltas and CLI overwrite refusal.
• Real portfolio CLI integration produced independent synthetic old/new PnL +34/+26 USD with immutable input/results and delta -8. No market effectiveness claim.
• Exact-head CI and CodeQL passed, including Linux Python 3.10–3.12 and Windows 3.12 (CI). No default-branch merge or deployment requested.

No credentials, paid data, generated research artifacts or live execution paths are added. Rollback is a revert of this additive change while preserving historical artifact pins. This PR implements authorized batch item 5; no separate issue is required.