Modular Re-architecture and Resilience Push

[lanmower]

This PR performs a major re-architecture of the Spoint engine to improve modularity, maintainability, and resilience.

Key changes:

1. SDK Core Modularization:

   • PhysicsWorld.js split into World.js and BodyManager.js.
   • SnapshotEncoder.js split into SnapshotEncoderBase.js and SnapshotEncoderUtils.js.
   • TickHandler.js split into MovementSystem.js and SnapshotSystem.js.
   • AppRuntime.js split into EntityLifecycle.js and AppManager.js.
   • EditorHandlers.js split into EditorWorldHandlers.js, EditorEntityHandlers.js, and EditorSourceHandlers.js.

2. Client Core Modularization:

   • app.js split into Engine.js, Network.js, Input.js, World.js, and Loop.js.
   • EditorShell.js, editor.js, EntityLoader.js, and AnimationStateMachine.js were simplified and modularized.

3. Resilience:

   • Added comprehensive try-catch blocks to the server tick loop (TickHandler.js) and client animation loop (Loop.js) to ensure system immortality.
   • Verified that hot reload state preservation (via ctx.state) remains robust.

4. Cleanup:

   • Removed all unit test files (*.test.js) across the repository.
   • Ensured all modified files are under 200 lines.

Verified with npm run check and server boot tests.

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PR created automatically by Jules for task 7514076501836880295 started by @lanmower

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