Negotiated portable observations

Use the opt-in remote outcome recipe when a consumer needs source effects, authentic server outcomes, evidence and recovery. The new outer protocol requires five authenticated transport operations and scoped evidence; old v2 packages and servers keep their contracts. Tools-first construction composes with C6 before Agent initialization. Unknown remote writes stop managed dispatch; session.getReceipt() repairs acknowledged source without action replay. Checkpoints restore observations, not workflow or budget authority. Repeated/concurrent receipt lookups reuse validated observations while still invoking the authenticated receipt transport. Missing authoritative metadata after source handoff remains unknown, including uninstrumented execution overrides. A failed shutdown completion callback preserves its error and releases settled ownership of the borrowed source Agent. See the recipe for repair, quota and cancellation details.