Clear the Persist Engine quality gate

[jonbaldie]

Parent

#27 — Bring production TypeScript to messcript's idiomatic ruleset

What to build

Both Persist Engine implementations pass the structural-quality gate while append-only recording, replay order, truncation, directory normalization, locking, and missing-file behavior remain recoverable and unchanged.

Acceptance criteria

• The Persist Engine production unit reports zero selected messcript findings under the pinned policy.
• Real file-system and in-memory tests verify append, replay, truncation, directory handling, locking, missing-file loading, and clearing an absent file.
• The refactor contains no source suppression or policy weakening.

Blocked by

• Pin messcript and define the production TypeScript gate #28 — Pin messcript and define the production TypeScript gate.