chore(release): 3.8.1

[acidkill]

Summary

Release 3.8.1. Version bumped across all 16 version-bearing locations, with a CHANGELOG.md
section for the two fixes that landed since 3.8.0.

PATCH rather than MINOR: both changes are bug fixes with no new surface. smem_transplant's
min_salience and the decay telemetry that would have justified a MINOR shipped in 3.8.0.

Contents

• fix(storage): persist the pre-compression neuron snapshot instead of dropping it #192 — save_neuron_snapshot sent a datetime into a column the schema declares as a
  string, so a SCHEMAFULL backend refused the write and the caller's fail-soft except
  hid it. Destructive compression therefore ran with no snapshot behind it.
• fix(memory): refresh content-derived fields on compress, restore, and refine #193 — compress, decompress, recover and instruction refinement now recompute
  content_hash, the stored embedding and metadata["_structure"] when they replace a
  neuron's content, batched per fiber rather than per neuron. Consumers of content-derived
  fields skip graph-only placeholder content instead of fingerprinting a store-wide constant.

Test plan

• python scripts/pre_ship.py — all 10 sections pass, including version consistency
  (16/16 at 3.8.1), the CHANGELOG entry check, ruff, mypy, the fast unit suite, and both
  documentation-freshness gates.
• Both merged PRs were green on all 9 CI checks before merge, including the live
  SurrealDB integration job.
• Post-publish: confirm the artefacts actually reached PyPI, npm (plugin and SDK),
  ClawHub and the VS Code Marketplace. The publish steps in release.yml are tolerant of
  failure, so a green job is not by itself evidence that anything was published.