[RohanFredriksson]

Batch 5 of ROADMAP.md, the last one. Batches 1–4 are already on master, so this targets master directly and contains one commit.

Changes

• Cloning: Entity::clone() and Entity::instantiate(json) copy an entity's saved state with new entity and component ids. Components that aren't serialisable are left out. Entity::load(json) still keeps the ids in the json, as scene loading needs.
• Prefabs (core/prefab.hpp): Prefab::save, load and spawn, and Pancake::spawn(file, position).
  • Files are cached and read again when their modified time changes.
  • Missing or malformed files print ERROR::PREFAB::... and return nullptr.
  • Prefabs don't include assets, so sprites they use must already be loaded (noted in the README).
• Inspector edit mode:
  • Dragging moves the selected entity and stops its body while held.
  • Duplicate and Delete buttons, with Ctrl+D and Delete shortcuts.
  • A toolbar to pause, step, save and load. Load adds the file's entities to the current scene, like the load command.
  • The actions are public as Inspector::duplicateSelected, deleteSelected and moveSelected.
• Hot reload:
  • TexturePool and AudioPool record each file's modified time, and AssetPool::reloadChanged() reloads changed files in place.
  • With Pancake::hotReload(true), the main loop checks twice a second of real time, so it also works while paused.
  • Texture::reload keeps the GL texture id, so sprites and spritesheets pick up the new image untouched. It also sets the unpack alignment for 3-channel rows that aren't 4-byte aligned.
• Console: clone <id|name> [x y], prefab <file> <x> <y>, saveprefab <id|name> <file>, hotreload [on|off] and reload.
• Demo: D no longer toggles physics debug drawing while Ctrl is held, since Ctrl+D duplicates in the inspector.
• Docs: README gets a "Prefabs and Hot Reload" section, CLAUDE.md gets "Prefabs and copies" and "Hot reload", and all ROADMAP.md items are ticked.

Testing

• New unit test tests/test_prefab.cpp covers:
  • clones getting new entity and component ids and dropping unsaved components;
  • load versus instantiate ids;
  • prefab save and load, with each load a new copy;
  • re-reading a changed prefab file;
  • missing, malformed and invalid prefab files.
• New engine test tests/test_editor_engine.cpp covers:
  • inspector duplicate, move (stopping the body) and delete;
  • prefabs from code and from the console, and clone;
  • hot reload of a PNG and a WAV that the test writes and then changes, checking the texture keeps its GL id;
  • reload with hot reload off.
• Not covered: real mouse dragging and button clicks in the inspector, since a mouse can't be driven in this environment. The tests call the same functions the drag and buttons use.
• All 14 tests pass locally in the ASan build and the Release build.

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https://claude.ai/code/session_015cNAkNqoDWA5gFReD1AsqV

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