Proposal: merge eos/services/{security,crypto} into eSec (3 milestones) #5

Proposal

Fold the security implementation from eos into this repository in three
gated milestones — no code moves until you approve:

1. In eos: land ADR-012 (Mbed TLS swap for hand-rolled AES/SHA/RSA/ECC);
   the EOS_ALLOW_STUB_CRYPTO stub gate disappears with real verification.
2. In eos: stabilize the eos/security.h + eos/crypto.h API surface
   (versioned, NIST-vector tests as contract).
3. The split: git subtree split of eos/services/security +
   eos/services/crypto into eSec, preserving history — only when an
   external consumer justifies independent versioning (§11 condition).

Undo path: subtree history preserved both sides; re-merge is
git subtree merge. Includes a PQC note (FIPS 203/204/205; verified
reference impls only per RustSec 2026-09-18).

Full text: docs/merge-proposal.md (this commit).

Triage

• docs: eSec is Implemented in eos, and one part is not #1 (status/scope docs): addressed by the current README — kept open as
  the tracking issue.
• Correct eSec implementation status and scope documentation #2: closed as duplicate of docs: eSec is Implemented in eos, and one part is not #1 (same author, same ask, shorter).