Add comprehensive technical documentation with architecture diagrams

[Copilot]

The codebase lacked structured documentation covering system architecture, data flows, and implementation details for developers and integrators.

Documentation Added

Created 9 interconnected markdown documents (~5,200 lines):

Core Architecture

• ARCHITECTURE.md - System components, design patterns, technology stack with component diagrams
• NODE_SYSTEM.md - Dataflow graph implementation: node types, type inference, graph traversal, visitor pattern
• COMPUTE_PIPELINE.md - OpenCL execution: device management, kernel generation, ray marching, memory hierarchy
• DATA_FLOW.md - End-to-end pipelines: model loading, rendering, slicing, resource caching with sequence diagrams

Integration & APIs

• 3MF_SUPPORT.md - Volumetric extension import/export: implicit namespace mapping, Image3D handling, resource dependencies
• API_REFERENCE.md - Public interface for C++/C#/Python with ACT-generated bindings, code examples per language
• DEVELOPER_GUIDE.md - Build setup, project structure, adding features (nodes, exporters, kernels), debugging workflows

Navigation

• README.md - Documentation index with use-case routing ("I want to..."), component map
• QUICK_REFERENCE.md - Common patterns: node creation, slicing, OpenCL kernels, testing, ImGUI widgets

Key Features

All documents include:

• Mermaid diagrams (20+) for architecture, sequences, state machines, flows
• Multi-language code examples where applicable
• Cross-references between related topics
• Performance considerations and bottleneck analysis

Example: Node Graph Construction

From QUICK_REFERENCE.md:

nodes::Model model;
model.createBeginEnd();

// Primitives
auto sphereId = model.addNode(std::make_unique<nodes::Sphere>());
auto boxId = model.addNode(std::make_unique<nodes::Box>());

// Boolean operation
auto unionId = model.addNode(std::make_unique<nodes::Union>());

// Connect: Begin → Sphere → Union → End
//                  Box ↗
model.connect(beginId, "cs", sphereId, "cs");
model.connect(sphereId, "distance", unionId, "a");
model.connect(boxId, "distance", unionId, "b");
model.connect(unionId, "result", endId, "input");

Architecture diagram shows data transformation pipeline:

3MF XML → Node Graph → OpenCL Source → Compiled Kernel → Image Buffer → Display

Documentation covers both high-level patterns and low-level implementation details (e.g., type inference rules, memory coalescing, marching cubes algorithm).

Original prompt

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This section details on the original issue you should resolve

<issue_title>Improve documentation </issue_title>
<issue_description>Please improve the documentation of the implementation. First create a list of interesting topics like classes, concepts data flows etc. than iterate through the list and create a detailed documentation for each topic. The documentation should be written in markdown and use GitHub compatible mermaid diagrams.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Improve documentation  #12

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