Adds the connection layer: spawnAgent + self-cleaning process registry,
env allow-list (no inherited process.env, KTD6b), redacted stderr capture
(S8), and connect() establishing a ClientSideConnection over ndJsonStream
and completing the initialize handshake with explicit integer protocol-
version negotiation (KTD2) under a timeout. fs capabilities advertised only
when toggled (KTD6); teardown is registry-SIGKILL-authoritative (KTD4a).
probe.ts adds an async readiness probe with a failure taxonomy. Includes a
minimal runnable echo-agent fixture and 25 unit tests.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>