[codex] Bundle agent-memory as single npm package

[gharibyan]

Summary

• Publish only the agent-memory npm package instead of individual @agent-memory/* packages.
• Mark internal workspace packages as private build units and bundle their compiled output into agent-memory/dist/internal/*.
• Update CI and publish workflows so package checks and npm publish target only agent-memory.
• Refresh docs, package-boundary tests, and release tests for the single-package contract.

Validation

• pnpm test -> 47/47 passing
• pnpm lint -> passing
• pnpm pack:check -> packs only agent-memory@0.0.0 with dist/internal/*

Notes

• The local untracked apps/openai-sqlite-demo/ folder was left out of the commit.