Clear the executable startup and shutdown quality gate

[jonbaldie]

Closes #36

What changed

• Renamed entrypoint-owned constants to satisfy the pinned structural policy while retaining the project’s Persist Engine vocabulary.
• Replaced development-only console calls with direct Deno stdout writes.
• Kept startup, binding, persistence loading/flushing, signal handling, and clean exit behavior unchanged.

Why

The executable entrypoint had constant-naming and development-code findings under the pinned messcript policy. This clears the unit gate without suppressions or policy changes.

Validation

• npm run quality:unit -- entrypoint
• deno lint main.ts
• deno test --frozen=false --allow-all tests/e2e_test.ts — 2 passed
• deno test --frozen=false --allow-all — 180 passed
• Live process smoke: OS-assigned port, /health 200, SIGTERM exit 0
• Two-axis review: Standards pass; Spec pass