start_session/dispatch_tool/end_session, mirroring sand-boxer's
SandboxExtension ABC one layer up: sand-boxer establishes where work
runs, this contract governs how an agent session runs on top of it.
Unblocks the rein-aharness parity proof (T04) and rein-openweights
bootstrap (T05).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Establishes glas-harness as the framework routing between concrete
harness backends ("reins"): rein-aharness (renamed from agent-harness)
and the newly chartered rein-openweights. GLAS-WP-0001 defines the
harness contract, rein registry, and a minimal gateway proving parity
against rein-aharness.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
