Expand game engine, replay, tests, and documentation

docs/architecture/components.md

@@ -222,11 +222,15 @@ is what makes the whole system testable without a server.
 
 **16. Replay viewer**
 
-- **Where:** Browser · **When:** after a game ends — **post-MVP**
-- **Does:** read-only projection over the stored event log, with playback controls.
-- **MVP: —** · **Final: S** · 0 → ~250 LOC
-- **Size driver:** small *because* it reuses component 14. Cheap only if events render standalone —
-  see [`overview.md`](overview.md#post-game-replay--a-desired-future-capability).
+- **Where:** Browser · **When:** after a game ends — **pulled forward, built**
+- **Does:** read-only projection over the event log, with playback controls. A Node script
+  precomputes one frame per visible event and writes a self-contained HTML file, so the browser
+  never runs the engine and there is no bundling or build step.
+- **MVP: —** · **Final: S** · 0 → ~250 LOC · *built: 560 LOC (replay) + 330 (narration)*
+- **Size driver:** the narration layer, not the rendering. Turning 30 event types into readable
+  sentences and deriving the "what is currently blocked" panel is most of it.
+- **Why it came early:** the open balance questions stopped being measurable and became judgment
+  calls. It also exercises much of component 14, which is MVP-critical either way.
 
 ### D. Dev-side