T2 Agent-addressed read checkpoint

Moved without content change from typescript-control-plane-migration-v0.md (former section "T2 Agent-addressed read checkpoint") on 2026-09-26; RFC baseline 3e443ad7c. Checkpoint records live in this ledger, not in the RFC body.

Todo list selection now composes with the existing typed summary-lanes batch. The Python role/status/id/Agent predicates and independent User scope rule are removed; legacy and promoted consumers share todos/agent_scope.ts with quota and decision scope. Explicit gate scope retains precedence over execution claim, while retained User claims now correctly restrict scoped list visibility. Full-source resume/succession stays evaluated before selection; original array ordinals survive filters and display limits. No extra selection runtime crossing, new capability/provider, or Python storage migration is introduced. Python keeps input normalization and rendering until their actual host consumers migrate. See the read contract; broader L5/D1 and local-default qualifications remain open.