docs: documentation sweep, replace ASCII with Mermaid, divide guides, and ASD-STE100 alignment

[spelech]

Summary of Changes

This pull request completes a comprehensive documentation sweep across both GitHub Pages (VitePress) and the repository, adhering to ASD-STE100 (Simplified Technical English) standards.

1. ASCII Art Replacement with Mermaid Diagrams & Screenshots

• **\README.md**:
  • Replaced UI ASCII mockup with a clean layout breakdown table and reference to \docs/images/dashboard_desktop.png.
  • Replaced ASCII system architecture box with a high-contrast Mermaid flowchart.
  • Replaced ASCII test metrics box with a structured Markdown table.
  • Bumped version to \�3.15.0.
• **\docs/index.md**:
  • Replaced dashboard ASCII box with the desktop screenshot and workspace component breakdown table.
• **\docs/ai-and-mcp/assistant.md**:
  • Replaced AI Assist interface ASCII mockup with a Mermaid flowchart layout.
  • Replaced staged attachments ASCII box with a Mermaid flowchart.
  • Replaced tool execution card ASCII box with a Mermaid sequence diagram and field specification table.
• **\docs/guide/collaborative-debugging.md**:
  • Replaced 4-tier ASCII block diagram with a detailed Mermaid flowchart.
• **\docs/TEST_COVERAGE.md\ & \docs/technical/test-coverage.md**:
  • Replaced ASCII test metrics with clean Markdown tables.
  • Replaced chunked test architecture diagram (\┌───┐, \▼) with a Mermaid flowchart.

2. Document Division & Modular Guides

• Divided monolithic guides into focused, dedicated documentation pages in VitePress and the repo:
  • **\docs/USER_GUIDE.md**: Converted from a monolithic 127-line text dump into a structured User Guide Hub linking to dedicated domain guides with Mermaid workflows.
  • **\docs/getting-started/test-flight.md**: New dedicated guide for the in-app Real Engine Test Flight runner.
  • **\docs/guide/companion-windows.md**: New dedicated guide for Magnetic Companion Windows (\WindowSnapManager), lockstep synchronization, proximity snapping, and drag detachment.
  • **\docs/getting-started/remote-access.md**: New modular guide for LAN IP discovery, SSH port forwarding, and Caddy reverse proxy setup.
  • **\docs/studio/lora-styles.md**: New modular guide for CivitAI LoRA art styles and prompt syntax.
  • **\docs/studio/comfyui-setup.md**: New modular guide for ComfyUI installation, 3D nodes (TRELLIS V2 / Hunyuan3D v2), and API workflow exports.
• Updated \docs/.vitepress/config.mts\ sidebar navigation to integrate all new guides into GitHub Pages.

3. Clear Setup & Installation for Testers and Distribution

• Added a prominent Testing & Setup Requirements Matrix in \README.md\ and \docs/getting-started/installation.md.
• Clearly separated:
  • Required Core Components: Self-contained .exe / installer, GPU / CPU, zero extra .NET runtime dependencies.
  • Optional Features: Ollama (LLM text), SD Forge (Images), ComfyUI (Video & 3D), Kokoro TTS (Speech), LiteLLM/Vertex AI (AI Assist), and Feature Packs (\�xt_*).

4. Corrections and New Feature Coverage

• Corrected \docs/getting-started/quickstart.md: Fixed the explanation directing users to select local Ollama models in the AI Assistant dropdown (clarifying that AI Assist connects to external gateways to preserve 100% of local GPU VRAM for generative models). Added options for testing via Real Engine Test Flight, REST API, and external chat frontends.
• Fleshed out new features: Magnetic Companion Windows, Real Engine Test Flight, LAN IP endpoints, and LiteLLM capability badges.

5. Quality & Compliance

• Formatted all revised procedural and descriptive text according to ASD-STE100 guidelines.
• Executed
  pm run lint\ and
  px tsc --noEmit\ (passed with 0 errors).
• Executed
  pm run docs:build\ (compiled VitePress site cleanly in < 4s with 0 syntax warnings).
• Ran full test suite (\dotnet test) with 212 tests passing.