chore: ignore all .venv*/ and venv*/ directories

feat(bbb): add SMILES validity guard with RDKit + test fixture

fix(core): apply level + propagate every call; tolerate pre-attached handlers

test(core): capture handler stream directly instead of monkey-patching caplog

feat(core): add shared structured logger with idempotent handler attach

chore: lock Python to 3.10–3.12 to match cp312-capped wheel availability

chore: pin runtime + dev dependencies for all three modalities

docs: tighten AGENTS.md — clarify Data Readiness checklist and storage boundary

docs: add AGENTS.md with vision, layout, standards, data readiness rules

chore: track planning docs and ignore .sixth/ tooling dir

chore: bootstrap NeuroBridge project skeleton