[release] Publish engram-subnet 1.0.0 to PyPI with stable API contract

[Dipraise1]

Context

pyproject.toml is at 0.1.2. ROADMAP Phase 2 calls for a stable engram-subnet 1.0.0 release with a stable API contract.

Tasks

• Audit the public SDK surface (engram/sdk/client.py, encryption.py, shamir.py, langchain.py, llama_index.py) and mark what is stable vs experimental
• Write a CHANGELOG and semver policy
• Verify optional extras install cleanly (arweave, media ingestion)
• Tag v1.0.0 and publish to PyPI (ideally via a release CI workflow)

From ROADMAP.md — Phase 2 'PyPI stable release'.