Deepgrain Foundry: move from a claude.ai artifact to a local repository

The game as of artifact version 24, ready for local development with
coding agents.

- Source split from three large files into 52 small ones under src/sim,
  src/render and src/ui, joined in the order in src/manifest.json by
  build.py. The joined code is unchanged apart from comments; every
  headless suite gives the same output, and screenshots in both looks
  are pixel-identical to before.
- Light tidying with no change in behaviour: one movement scan loop,
  shared hazard-stripe and belt shader helpers, unused code removed, a
  shared check helper for the test suites.
- World files can be exported as an ordinary download outside claude.ai.
- Tests: broken old scripts removed, experiments moved to tools/,
  test/run_all.py added. Tools: shot.py (repeatable screenshots),
  where.py, map.py.
- Docs: AGENTS.md, CLAUDE.md, NOTES.md (the owner's to-do inbox),
  docs/PROJECT_MAP.md, DESIGN.md, TESTING.md, systems notes, the
  owner's requests and an agent log.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01K9kLmYADKSEjuwUN3rFxDA

README.md

@@ -0,0 +1,64 @@
+# Deepgrain Foundry
+
+A falling-sand factory game in the browser, in the style of Sandustry.
+
+Every grain of sand, ore, water and fire is simulated. You fly a small bot over a side-view
+world, dig with a resonance drill and vacuum up what breaks loose. You build furnaces from
+blocks, melt ore with coal and air, and cast the metal in molds. Then you sell bars, alloys and
+other goods at a trade dock, automating with belts, screw tubes, filters, fans, pipes and
+machines, until the land claim is paid off and beyond.
+
+## Play
+
+```sh
+python3 build.py
+python3 -m http.server -d dist     # then open http://localhost:8000
+```
+
+Opening `dist/index.html` directly works too. The game is one self-contained page with no
+downloads; sound and graphics are all generated in code. Saves stay in your browser.
+- To keep or move a world, use Pause → Export world file.
+- To load one, use Settings → Load a world file on the title screen, or Pause → Import world file
+  during a game. World files exported from the claude.ai version load here too.
+
+The controls are in the in-game notebook (N) under Controls. The basics:
+- WASD to fly;
+- 1–4 for the drill, vacuum, build and igniter;
+- left and right mouse to use the tool;
+- Q/E and R to change what it does;
+- F to use things;
+- Esc for the menu.
+
+## Develop
+
+You need Node (tested with 22), Python 3, and Playwright for the browser tests and screenshots:
+
+```sh
+pip install -r requirements.txt
+python3 -m playwright install chromium
+```
+
+```sh
+python3 build.py                     # build dist/index.html
+python3 test/run_all.py              # headless test suites
+python3 test/run_all.py --browser    # plus the browser tests
+python3 tools/shot.py shots/x.png --setup tools/scenes/clear-sky.js   # a screenshot
+```
+
+The source is small JavaScript files with no dependencies or bundler:
+- `src/sim/`: the simulation;
+- `src/render/`: drawing;
+- `src/ui/`: the browser shell.
+
+`build.py` joins them in the order given in `src/manifest.json`.
+
+## Documents
+
+- `AGENTS.md` / `CLAUDE.md`: how coding agents work on this project.
+- `NOTES.md`: the to-do list.
+- `docs/PROJECT_MAP.md`: where everything is.
+- `docs/DESIGN.md`: what the game is meant to be, and the decisions made.
+- `docs/TESTING.md`: tests, screenshots and pitfalls.
+- `docs/systems/`: notes on individual systems.
+- `docs/history/requests.md`: the owner's requests while the game was built.
+- `docs/agent-log.md`: the work log.