feat: add autonomous team execution and causal recovery

[douglas-grishen]

What changed

• add the opt-in @agentplat/collective-runtime/team-execution public subpath
• execute activated team position DAGs through prepared, replay-idempotent dispatches
• retain only content-addressed artifact references and verify local availability
• adapt controlled portable-agent sessions without widening Work authority
• emit exact failure/unsafe/expiry evidence and project it into Team Formation
• rebind a replacement epoch while retaining only the unaffected completed subgraph
• add CAS storage, bounded state, cancellation, handoff, strict validators and canonical domains
• document architecture, implementation boundaries and the security model

Why

Dynamic team formation previously stopped at roster selection and joint contract activation. Applications still needed a provider-neutral way to run the team graph, exchange verifiable outputs and recover causally from one failed member without introducing a central scheduler or shared team authority.

Impact

This is additive and opt-in. Existing Mesh, Work Contract, portable-agent and single-assignee behavior are unchanged. Dispatches and joint contracts remain coordination records; individual Work Contracts, leases, epochs and fencing tokens remain authoritative at effect gateways.

Validation

• full workspace build and type-check across 48 packages
• full unit suite: 890 tests / 894 assertions, 887 passed, 0 failed, 1 skipped, 6 todo
• packed release smoke: 48 tarballs and 98 API surfaces
• dedicated Team Execution packed consumer
• public package catalog and API contract checks
• public audit: no secret findings or restricted terminology
• Prettier and git diff --check

Stack

Base: codex/dynamic-team-formation-v1 (the Team Formation capability this runtime composes).