Upgrade README to professional open-source standard

[Copilot]

Transformed README from functional technical document to professional project introduction following modern open-source conventions.

Changes

Structure & Navigation

• Centered header with license/language badges and quick navigation menu
• Table of contents with 25+ anchored sections
• Reorganized content flow: Overview → Problem/Solution → Features → Architecture → Quick Start

New Sections

• "Why HLV-RAPS?" - Problem statement and value proposition
• "Key Features" - Categorized by Safety, Predictive, Observability, Portability
• "Quick Start" - Prerequisites, build instructions, demo commands
• "Repository Structure" - Visual tree + component table
• "Contributing" - Step-by-step process with guidelines
• "Citation" - BibTeX format for academic use

Visual Enhancements

• ASCII architecture diagram showing component relationships
• Emoji icons for section scanning (🔮 Predict, ✅ Validate, ⚡ Execute, 📝 Audit)
• Structured tables for documentation index and component mapping
• Checkmark/X-mark comparison lists

Content Improvements

• Code examples: 1 → 4 (clone, build, test, run demos)
• Consolidated "What/Why/How" narrative
• Added prerequisites and platform requirements
• Expanded contributing guidelines with fork/branch/PR workflow

Metrics

Lines:           375 → 555 (+48%)
Sections:        ~15 → ~25
Navigation:      0 → 30+ internal links
Code blocks:     1 → 4
Visual elements: Minimal → Rich (badges, emojis, diagrams, tables)

All documentation links and directory references validated.

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[Copilot]

Pull request overview

This PR transforms the README from a technical reference document into a professional, modern open-source project introduction. The upgrade significantly improves navigation, structure, and presentation while maintaining technical accuracy.

Changes:

• Added comprehensive navigation with badges, quick links, and a detailed table of contents with 25+ anchored sections
• Introduced new sections including "Why HLV-RAPS?", "Key Features", "Quick Start", "Repository Structure", and "Contributing"
• Enhanced visual presentation with ASCII architecture diagrams, emoji icons, structured tables, and formatted code examples
• Expanded documentation with prerequisites, build instructions, demo commands, BibTeX citation format, and full license text

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[Copilot]

The repository structure diagram shows only hlv_demo/ and api_client/ under examples, but the directory also contains hil/ and sil/ subdirectories. The examples/hil/hil_readiness_check.cpp file is explicitly referenced later in the README (line 405). Consider adding these directories to the structure diagram for completeness, or add a note that the diagram shows only key directories.

Suggested change

	│ └── api_client/ # REST API client examples
	│ ├── api_client/ # REST API client examples
	│ ├── hil/ # Hardware-in-the-loop examples
	│ └── sil/ # Software-in-the-loop examples