admit OMP 18.1 after live delivery probes

[schickling-assistant]

Summary

• admit the OMP 18.1 minor series after measuring 18.1.2
• keep new minors, prereleases, ambiguous banners, and major versions fail-closed
• record the five delivery-critical checks and exact live evidence

Verification

• extension API and lifecycle vocabulary unchanged
• idle edge remains post-agent_end
• approval events retain a correlating toolCallId
• shipped st2 driver omp-session path completed a real delivery turn
• nix develop -c cargo test --lib omp_session::tests (14 passed)
• nix develop -c cargo build --bin st2
• git diff --check

Posted on behalf of @schickling

field	value
agent_identity	dev3.direct.omp.5wtg9j4p
session	dev3.5wtg9j4p
agent_persona	generalist
agent_supervisor	unavailable
agent_tool	OMP
agent_tool_version	18.0.11
agent_runtime	OMP 18.0.11
tooling_profile	dotfiles@2161b9c