[CanReader]

What this changes

Registers Game/assets/shaders with the engine's new shader hot reload, so in Debug builds saving a game shader (voxel, water, the GL gbuffer_gl / lighting_pass_gl overrides) updates the running game. The game folder is registered after the engine's, so the game's copy of an overridden shader is the one that reloads.

Merge CanReader/SleakEngine#224 first. This uses the new Debug/ShaderHotReload.hpp, and CI for PRs into staging builds against the engine's staging branch, so CI here fails until the engine PR is merged. Re-run it after that.

Why

Edits to block and water shaders needed a rebuild and restart. Follow-up for owning the block look in deferred mode: #89.

How it was verified

• Builds on Linux
• Loaded a world and played it (-world capbase, Vulkan with --validate and OpenGL), editing game shaders live while it ran
• Placed and broke blocks
• Saved, quit, reloaded, and the world was intact

Placing, breaking and saving weren't exercised; this change only adds a Debug-only call in Game::Initialize() and a compile definition.

Checklist

• Shader changes updated all backend variants and the committed .spv (no shader changes)
• Save format changes bumped WorldMeta::CURRENT_VERSION and handle old worlds (no save changes)
• Collision changes kept the single-pass MTV resolution intact (no collision changes)
• New event handlers are unregistered on scene teardown (no new handlers)