[arudaev]

What and why

python scripts/export_stage.py turns art/stages/ into what the game loads. It writes game/public/assets/stages/<region>/stage.json, the docs/13 manifest Vatsal's loader (#24) and collision (#34) read, and copies every layer plate and collision file next to it.

• Manifest shape. Chunks with grid x/y; per state, the layers in draw order with z (the docs/04 role), scroll and file, plus the state's collision file. Draw in list order: Rusty Creek's soft water goes last, exactly as creek_layers.py composes it. docs/13 now spells the shape out.
• Config. Each region has an export.json. Rusty Creek: 3 chunks, clean (clean architecture) and anomaly (supports and traversal), with the right chunk reusing the left's shared plates, each copied once. Hidden Garden: hg-0-0 from split_layers.py.
• Generated, not committed. The plates already live in art/stages/; copying them would add 18 MB of byte-identical files. game/public/assets/stages/ is in .gitignore. The export needs only the standard library, so once [1/4] chore(shared): scaffold the phaser game runtime #94 is on main, predev/prebuild in game/package.json can run it. That's a small shared-file PR after the merge.
• --verify rebuilds every state from the exported files in manifest order and compares it with the region's composed art. It now runs in the art CI.

Issue

Closes #109

Stack

• [4/4] this PR ← base chore/85-hidden-garden-collision
• [3/4] feat: add the Hidden Garden collision and Dexter's waypoints #106 [3/4] feat: add the Hidden Garden collision and Dexter's waypoints
• [2/4] art: draw the Hidden Garden prologue chunk and its layers #105 [2/4] art: draw the Hidden Garden prologue chunk and its layers
• [1/4] feat: split composed stage chunks into the layer stack #104 [1/4] feat: split composed stage chunks into the layer stack ← base main

Merge bottom up with merge commits; retarget the next PR to main before merging it.

Verification

• python scripts/export_stage.py --verify: rusty-creek has 3 chunks, 6 states and 19 files; hidden-garden has 1 chunk, 1 state and 5 files. All 7 states are rebuilt exactly.
• python -m unittest discover -s scripts -p "test_*.py": 5 new tests (manifest, shared plates copied once, verify catches a wrong draw order, bad config, the committed regions).
• python scripts/check_docs.py
• Rusty Creek's collision isn't on this branch yet (feat: add Rusty Creek collision with a reach checker #97). Once feat: add Rusty Creek collision with a reach checker #97 is merged, the same export picks it up with no change.