Complete learning checks and local report export

[maximalfocus]

Summary

• add accessible learning checks for the causal loop, intervention, and provenance distinctions
• generate a deterministic paired report with configuration, events, provenance, final state, metrics, differences, assumptions, and limitations
• export the report as a browser-local portable JSON file
• add a full guided release-acceptance test from replay through comparison, learning, and export

Verification

• npm test — 28 tests passed
• npm run typecheck — passed
• npm run lint — passed
• npm run build — passed
• npm audit --audit-level=high — 0 vulnerabilities
• local Vite startup and HTTP load — passed
• safety scan — no networking or process-execution APIs in src

Closes #9