Better directory structure for docs - reorganize documentation and streamline README

[Copilot]

This PR addresses the documentation organization issues identified in the repository by creating a proper directory structure and streamlining the root README.md.

Changes Made

📁 Created organized documentation structure

• New docs/ directory with logical subdirectories:
  • docs/architecture/ - Architecture and design documentation
  • docs/extensions/ - Extension-specific documentation
  • docs/testing/ - Test guides and references

📝 Moved scattered documentation files

• COMPLETE_PROGRAM_TESTS.md → docs/testing/complete-program-tests.md
• CONFIGURATION_TESTING.md → docs/testing/configuration-testing.md
• C_EXTENSION.md → docs/extensions/c-extension.md
• TESTS.md → docs/testing/instruction-tests.md
• sim/README.md → docs/testing/simulation.md

🎯 Streamlined root README.md

• Reduced from 276 lines to 133 lines (52% reduction)
• Focused on essential information: key features, architecture overview, quick start
• Improved discoverability: clear links to detailed documentation
• Added missing architecture section: comprehensive processor architecture overview
• Better visual organization: badges, emojis, structured sections

📋 Added documentation navigation

• Created docs/README.md as documentation index
• Added docs/architecture/overview.md with detailed processor architecture
• Updated cross-references between documentation files

Before & After

Before: Documentation scattered across root directory, 276-line README with excessive detail obscuring the project's purpose

After: Clean root directory with organized docs structure, concise README focusing on architecture and getting started

Repository Structure

vigna/
├── vigna_core.v              # Main processor RTL
├── vigna_coproc.v           # Coprocessor for M extension
├── vigna_conf*.vh           # Configuration files
├── vigna_axi.v              # AXI4-Lite bus adapter
├── Makefile                 # Build system
├── docs/                    # 📁 Documentation
│   ├── architecture/        # Architecture and design docs
│   ├── extensions/          # Extension documentation  
│   └── testing/             # Test guides and references
├── sim/                     # 🧪 Test suite and testbenches
├── programs/                # 📝 C test programs
└── tools/                   # 🛠️ Utility scripts

The documentation now provides a much clearer entry point for users while maintaining all detailed information in an organized, discoverable structure.

Fixes #19.

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[helium729]

Add documentations for other supported extensions like M and Zicsr, also write about interrupts @copilot

[Copilot]

Add documentations for other supported extensions like M and Zicsr, also write about interrupts @copilot

Added comprehensive documentation for M extension, Zicsr extension, and interrupt handling. Created:

• docs/extensions/m-extension.md - Complete M extension implementation with multiply/divide instructions
• docs/extensions/zicsr-extension.md - CSR instruction set and machine-level CSR reference
• docs/architecture/interrupts.md - Interrupt handling architecture with hardware interrupt sources and CSR-based management

All documentation includes implementation details, configuration examples, and programming guidance. Commit: c05e676

[Copilot]

Pull Request Overview

This PR reorganizes the project's documentation by introducing a structured docs/ directory, relocating existing documentation files into appropriate subdirectories, and condensing the root README.md to focus on key information.

• Created a clear directory layout under docs/ with subdirectories for architecture, extensions, and testing
• Moved legacy documentation files into the new docs/ hierarchy
• Streamlined the top-level README.md and added a dedicated docs/README.md as an entry point

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
docs/testing/simulation.md	Updated step wording to refer to the project root directory
docs/extensions/zicsr-extension.md	Added detailed Zicsr extension implementation document
docs/extensions/m-extension.md	Added detailed M extension implementation document
docs/architecture/overview.md	Added high-level processor architecture overview
docs/architecture/interrupts.md	Added comprehensive interrupt handling documentation
docs/README.md	Created documentation index with links to subdirectories
README.md	Condensed root README and updated integration examples

Comments suppressed due to low confidence (3)

docs/README.md:12

• [nitpick] The term 'Compact instruction extension' could be misleading. Consider using 'Compressed instruction extension' to align with the official RISC-V naming for the C extension.

- [C Extension](extensions/c-extension.md) - RISC-V Compact instruction extension support

README.md:39

• [nitpick] The '+Zicsr' label in the configuration table may be ambiguous; consider renaming it to 'Zicsr Extension' or integrating it as a column header for clarity.

| +Zicsr        | Any  | Any      | Any        | Any       | ✓   |

README.md:106

• The port name '.reset' does not match the earlier interface which uses '.resetn'. Update this to '.resetn(resetn)' to match the actual signal name.

.reset(reset),