Establish one canonical subject and follow it through every observable surface.

A projection is a derivation, not a second source of truth. The projection-repro surface takes one canonical subject, replays the durable event log, and projects the resulting state to a chosen visualization. If the projection is deleted, the next rebuild produces the same artifact. No external effect is re-executed.

Three phases: replay, project, reconcile.

1. Replay — Read the durable event log and re-derive the canonical ECS world. The replay is deterministic; it does not call any provider, device, or network.
2. Project — A renderer (the projection) reads the world and produces a typed view. The view is independent of the surface; the same world can be projected to HTML, JSON, or a visualization.
3. Reconcile — The renderer compares the projection to the live surface and applies a minimal diff. On the SSG, the surface is the file system; on the browser, the live DOM.

The result is a representation that survives process restarts, matches the canonical world, and is the only path that produces visible state.

What is implemented today.

• Replay — the durable event log is read; the canonical world is re-derived.
• Projection — the world is projected to the chosen surface.
• Reconcile — the projection is diffed against the live surface and a minimal change is applied.

The SSG runs this loop at build time. The browser hydration runs the same loop with a live DOM substrate.