Add preregistration consistency assistant

[haocyan0723-code]

/claim #16

This adds a focused preregistration consistency assistant for AI research review output.

Scope:

• checks preregistration id coverage
• checks primary outcome reporting
• blocks unlogged primary outcome changes
• blocks unexplained analysis plan changes
• blocks unplanned subgroup claims that are not marked exploratory
• flags sample-size shortfalls
• flags secondary outcome promotion and missing null-result discussion
• includes MP4 and GIF demo artifacts for review

Validation run locally:

• node preregistration-consistency-assistant/test.js
• node preregistration-consistency-assistant/demo.js
• node --check preregistration-consistency-assistant/index.js

No external registries, private manuscripts, AI APIs, credentials, or payment systems are used.