docs: update README file map for split runtime (#169)

README.md documented game.js as a single-file core engine, but the
runtime was split into 10 modules under js/. Updated the file map
to reflect the current architecture.

README.md

@@ -104,8 +104,18 @@ This game is a **decision simulator** for our actual work.
 
 ## Files
 
-- `index.html` — Game UI
-- `game.js` — Core engine (tick loop, buildings, projects, events)
+- `index.html` — Game UI + script loader
+- `js/` — Split runtime (10 modules):
+  - `data.js` — Game data, project/upgrade/event definitions
+  - `utils.js` — Shared helpers
+  - `combat.js` — Combat and threat resolution
+  - `strategy.js` — Strategic decision logic
+  - `sound.js` — Audio engine
+  - `engine.js` — Core tick loop and state management
+  - `render.js` — DOM rendering and UI updates
+  - `tutorial.js` — Tutorial/onboarding flow
+  - `dismantle.js` — Dismantle/teardown mechanics
+  - `main.js` — Entry point, init, and game start
 - `DESIGN.md` — Full design document with narrative arc and mechanics
 - `README.md` — This file