v2.4.3 — OCSF version self-correct + log-level env var + fastembed preload

Patch release preparing v2.4.3 for Growth Week 2 launch. Three instrumentation and developer-experience improvements.

Highlights

• feat: OCSF version self-correct (#96) — ocsf_version field now dynamically resolved from the installed ocsf-schema package at import time rather than hardcoded. Eliminates version skew after OCSF package updates.
• feat: ZETTELFORGE_LOG_LEVEL env var (#96) — structlog threshold respects the environment variable, consistent with other ZETTELFORGE_* overrides.
• feat: Fastembed preload (#96) — Embedding model loaded eagerly on first MemoryManager init rather than on first recall, reducing remember() latency on cold-start queries.

Upgrade action (Vigil)

Bump Vigil's ZettelForge pin to 2.4.3 and restart. The ZETTELFORGE_LOG_LEVEL env var lets you silence DEBUG noise in production without code changes.

See CHANGELOG.md for the full set of changes.