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

tools/where.py

@@ -0,0 +1,37 @@
+#!/usr/bin/env python3
+"""Turn a line number in dist/index.html into the source file and line it came from.
+
+  python3 tools/where.py 4211          ->  src/sim/pipes.js:57
+  python3 tools/where.py < error.txt   ->  the text with every index.html:LINE rewritten
+
+Browser errors point into the built page. build.py writes dist/bundle-lines.json, which says where
+each source file starts in it. Rebuild first if the sources changed since the error.
+"""
+import json, pathlib, re, sys
+
+ROOT = pathlib.Path(__file__).resolve().parent.parent
+
+
+def load():
+    return json.loads((ROOT / 'dist' / 'bundle-lines.json').read_text())['files']
+
+
+def where(line, files=None):
+    files = files or load()
+    best = None
+    for start, f in files:
+        if start <= line: best = (start, f)
+        else: break
+    return f'src/{best[1]}:{line - best[0] + 1}' if best else f'index.html:{line} (before the script)'
+
+
+def translate(text, files=None):
+    files = files or load()
+    return re.sub(r'(?:file://)?[^\s()]*index\.html:(\d+)(:\d+)?', lambda m: where(int(m.group(1)), files) + (m.group(2) or ''), text)
+
+
+if __name__ == '__main__':
+    if len(sys.argv) > 1:
+        for a in sys.argv[1:]: print(where(int(a)))
+    else:
+        print(translate(sys.stdin.read()), end='')