[EPIC] Runtime Skeleton — the first executable milestone

[ucguy4u]

Problem

Nine phases of runtime, each with its own plan, is nine chances to define a runtime rather than build one. Every subsystem after the first should plug into an existing runtime instead of inventing its own lifecycle, its own storage assumption, and its own idea of where state lives.

That is not hypothetical — DriftMeetingRepository, features/coins/, features/money/, and relational_store each did exactly that, because there was no runtime to plug into.

Expected outcome

The first executable milestone. One thing proven end to end:

Operation → Persist → Replay → Projection → UI

Scope — deliberately small

In	Out
Supervisor	AI
Vault	Sync
Operation Log	Workflows
Runtime API (the six functions)	Capabilities beyond a minimal Notes reference
Empty Projection Engine	Everything else

The projection engine is empty on purpose. It proves the seam exists and that a projection can be driven, rebuilt, and dropped. What it projects comes later.

Why this ordering

Every subsystem after the skeleton inherits a runtime that already has a lifecycle owner, a storage contract, and a public surface. Nothing after this has to decide where state lives, because that question is answered and enforced.

The Supervisor and the replay engine are the two architectural centres of Airo Mind (design spec §11c-3). A skeleton containing both, and nothing else, is the smallest thing that can prove them.

Definition of done

• The runtime boots with only the Supervisor — condition 1 of [EPIC] Runtime v1 — architecture complete: the ten conditions #1311
• A Notes capability emits an operation through emit_operation and nothing else
• The operation persists, replays, and drives a projection
• The projection is deleted and rebuilt with zero data loss — C4
• The UI renders from the projection, not from the log
• replay_passes == 1 is asserted, not documented — C2
• The capability holds no durable storage of its own — I2, I4
• Every gate in the mandatory review pipeline passes

What this replaces

Not the phase plans — it sequences them. Phases 1–6 still deliver what they describe; the skeleton is the vertical slice through them that must work before any of them is finished horizontally.

Blocked by

Phase 1 (#1193) and the Supervisor (#1302).