Chore/document deterministic nlp contract

[AAdewunmi]

Summary

Documents the deterministic NLP contract for StudyBuddy insights and adds a Sprint 3 Day 1 verification runbook.

Changes

• Revised docs/ai-nlp-contract.md to match the current StudyInsight model.
• Clarified that StudyInsight inherits ownership through session.owner.
• Updated uniqueness documentation to session + source_hash.
• Separated current implemented scope from planned Sprint 3 NLP pipeline work.
• Documented deterministic non-LLM direction for summary, keywords, confidence, explanation, and source hashing.
• Added executable Sprint 3 Day 1 runbook at docs/sprint-runbook/sprint-3/sprint-3-day-1.sh.

Behaviour

The docs now describe the current persisted insight foundation accurately and avoid overclaiming selectors, views, templates, or NLP pipeline behaviour that has not been implemented yet.

Why

The previous NLP contract still reflected an older design with a separate StudyInsight.owner field. The updated contract matches the current session-owned model and gives Sprint 3 a reliable verification path.

Validation

Ran the Sprint 3 Day 1 runbook:

apps/insights/tests/test_models.py passes with 7 tests.
apps/insights tests pass with 9 tests.
121 passed in 3.20s
Sprint 3 Day 1 verification complete.

Result

The deterministic NLP contract and runbook are aligned with the current Django project state.

Notes

The feature remains intentionally non-LLM for the MVP. The contract marks NLP utilities, selectors, views, and UI behaviour as planned Sprint 3 work rather than current implementation.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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