Refactor graph correlation scoring pipeline

[viamus]

Summary

• extract deterministic graph correlation helpers into onebrain.core.correlation for facets, scoring, graph operations, and grouping
• keep the existing no-GenAI graph aggregation behavior while adding deterministic-v1 score metadata to edges, grouping opportunities, aggregate memories, and links
• add focused tests for score versioning, facet extraction, grouped centroid metadata, and merged entity/facet/vector evidence
• document the deterministic pipeline, score-version guidance, graph aggregation flags, and corpus-lab experiment flow

Wiki sync

• pushed public GitHub Wiki update separately to viamus/one-brain.wiki.git at commit 796ee6a

Validation

• uv run ruff format backend/src/onebrain/core/correlation backend/src/onebrain/core/application/service.py backend/tests/test_correlation.py backend/tests/test_graph.py
• uv run ruff check backend/src/onebrain/core/correlation backend/src/onebrain/core/application/service.py backend/tests/test_correlation.py backend/tests/test_graph.py
• uv run pytest backend/tests/test_correlation.py backend/tests/test_graph.py backend/tests/test_django_jobs.py -q
• uv run pytest -q

Note

• npm run web:typecheck was attempted but the local workspace is missing tsc/frontend node_modules, so it failed before typechecking. This PR does not change frontend code.