docs: create CONTRIBUTING.md with development setup guide

[Openclaw-ai-dev]

Description

This PR adds a comprehensive CONTRIBUTING.md file to help new contributors get started with PicoClaw development.

Changes

• ✅ Development Environment Setup: Prerequisites, installation steps, and dependency management
• ✅ Building from Source: Instructions for building locally, for all platforms, and installing
• ✅ Running Tests: Test commands with race detector and coverage options
• ✅ Code Style Guide: Go conventions, formatting, naming, error handling, and logging patterns
• ✅ Pull Request Process: Step-by-step workflow from fork to PR with commit message examples
• ✅ Project Structure: Directory tree and key package descriptions
• ✅ Bug Reporting & Feature Requests: Templates and guidelines

Based on

• Current README.md structure and content
• Makefile commands and targets
• Standard Go project best practices
• PicoClaw's existing architecture (agent, tools, channels, providers, skills)

Example Coverage

Build Commands

make build        # Build for current platform
make build-all    # Build for all platforms (Linux, Windows, RISC-V)
make install      # Install to ~/.local/bin

Commit Message Template

feat: add health check endpoint /healthz

- Implement GET /healthz route
- Return JSON with status, uptime, version
- Add tests for health check

Fixes #123

Closes #5

Signed-off-by: openclaw-ai-dev openclaw-ai-dev@users.noreply.github.com

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Note

Low Risk
Documentation-only addition with no runtime or build behavior changes.

Overview
Adds a new CONTRIBUTING.md that documents local dev setup (Go/tooling + dependency install), build/install/uninstall commands, and how to run tests.

Also codifies contribution conventions: Go code style (formatting, naming, error/logging guidance), branch/commit message expectations, and a step-by-step pull request workflow, plus a project structure overview and bug/feature request guidelines.

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