Add causal claim validity guard

[pine-harbor]

/claim #16

Summary

Adds causal-claim-validity-guard/, a self-contained causal-claim review gate for issue #16's AI-Powered Research Assistant Suite.

The module reviews synthetic manuscript packets before AI peer-review output is trusted, with checks for:

• causal-language overreach
• study-design/evidence mismatch
• missing comparator or counterfactual support
• temporal-order gaps
• missing confounder strategy
• unreported effect-size uncertainty
• underpowered subgroup causal claims

It emits deterministic RELEASE, REVISE, or HOLD decisions with evidence-linked remediation notes.

Demo

Short demo video included in the PR:

• causal-claim-validity-guard/artifacts/demo.mp4

Generated reviewer artifacts:

• causal-claim-validity-guard/artifacts/causal-claim-review.json
• causal-claim-validity-guard/artifacts/causal-claim-review.md
• causal-claim-validity-guard/artifacts/causal-claim-summary.svg

Validation

Ran locally:

cd causal-claim-validity-guard
npm test
npm run demo
npm run check
npm run video
git diff --check

Results:

• npm test: 4 tests passed.
• npm run demo: generated 4-packet review report with RELEASE: 2, REVISE: 1, HOLD: 1.
• npm run check: syntax checks passed.
• npm run video: generated 8-second H.264 MP4 demo.
• git diff --check: passed.

MP4 verification:

• H.264 video, 1280x720, 16:9.
• 8.000 seconds.
• 30 fps, 240 frames.

Scope / Safety

• No external APIs.
• No credentials.
• No private manuscripts.
• No live datasets.
• Synthetic review packets only.
• Dependency-free Node implementation.

Implemented with Codex assistance and locally verified before submission.