docs: document integration, development, CI/CD, and security practices

- Add a comprehensive guide for Claude Code integration, covering project architecture, main types, key methods, authentication, proxy support, and configuration patterns
- Document development commands for testing, formatting, linting, and SSH test server setup
- Detail CI/CD procedures, including testing environment, workflows, and code quality tools
- Provide usage examples and dependency list
- Summarize security features and configuration options

Signed-off-by: appleboy <appleboy.tw@gmail.com>

Author: appleboy

CLAUDE.md

@@ -0,0 +1,138 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+easyssh-proxy is a Go library that provides a simple SSH client implementation with support for SSH tunneling/proxy connections. It's forked from the original easyssh project with additional features for proxy connections, timeout handling, and secure key management.
+
+## Core Architecture
+
+### Main Types
+
+- **MakeConfig**: Primary configuration struct containing SSH connection parameters (user, server, keys, timeouts, proxy settings)
+- **DefaultConfig**: Configuration struct used for SSH proxy/jumphost connections
+- Both structs share similar fields but MakeConfig includes additional proxy capabilities
+
+### Key Methods
+
+- `Connect()`: Establishes SSH session and client connection
+- `Run()`: Executes single command and returns output
+- `Stream()`: Executes command with real-time streaming output via channels
+- `Scp()`: Copies files to remote server
+- `WriteFile()`: Writes content from io.Reader to remote file
+
+### Authentication Support
+
+- Password authentication
+- Private key files (with optional passphrase)
+- Raw private key content (embedded in code)
+- SSH agent integration
+- Custom cipher and key exchange algorithms
+
+### Proxy/Jumphost Architecture
+
+The library supports SSH proxy connections where traffic is tunneled through an intermediate server:
+
+```text
+Client -> Jumphost -> Target Server
+```
+
+The `Proxy` field in MakeConfig uses DefaultConfig to define the jumphost connection parameters.
+
+## Development Commands
+
+### Testing
+
+```bash
+make test                    # Run all tests with coverage
+go test -v ./...            # Run tests verbose
+```
+
+### Code Quality
+
+```bash
+make fmt                     # Format code using gofumpt
+make vet                     # Run go vet
+```
+
+### SSH Test Server Setup
+
+```bash
+make ssh-server             # Setup local SSH test server (Alpine Linux)
+```
+
+### Linting
+
+The project uses golangci-lint via GitHub Actions. No local lint command is defined in the Makefile.
+
+## Testing Infrastructure
+
+### Test Environment
+
+- Uses Alpine Linux container with SSH server setup
+- Creates test users: `drone-scp` and `root`
+- SSH keys located in `tests/.ssh/` directory
+- Test files in `tests/` include sample data and configuration
+
+### CI/CD
+
+- GitHub Actions workflow in `.github/workflows/testing.yml`
+- Runs tests in Go 1.23 Alpine container
+- Includes golangci-lint for code quality
+- Codecov integration for coverage reporting
+
+## Code Patterns
+
+### Configuration Pattern
+
+```go
+ssh := &easyssh.MakeConfig{
+    User:    "username",
+    Server:  "hostname",
+    KeyPath: "/path/to/key",
+    Port:    "22",
+    Timeout: 60 * time.Second,
+}
+```
+
+### Proxy Configuration
+
+```go
+ssh := &easyssh.MakeConfig{
+    // ... main server config
+    Proxy: easyssh.DefaultConfig{
+        // ... jumphost config
+    },
+}
+```
+
+### Error Handling
+
+Functions return multiple values following Go conventions:
+
+- `Run()`: (stdout, stderr, isTimeout, error)
+- `Stream()`: (stdoutChan, stderrChan, doneChan, errChan, error)
+
+## Example Usage
+
+Comprehensive examples are available in `_examples/` directory:
+
+- `ssh/`: Basic command execution
+- `scp/`: File copying
+- `proxy/`: SSH tunneling through jumphost
+- `stream/`: Real-time command output streaming
+- `writeFile/`: Writing content to remote files
+
+## Dependencies
+
+- `golang.org/x/crypto/ssh`: Core SSH protocol implementation
+- `github.com/ScaleFT/sshkeys`: Enhanced private key parsing with passphrase support
+- `github.com/stretchr/testify`: Testing framework
+
+## Security Considerations
+
+- Supports both secure and insecure cipher configurations
+- `UseInsecureCipher` flag enables legacy/weak ciphers when needed
+- Fingerprint verification available for enhanced security
+- Private keys can be embedded as strings or loaded from files