feat: set logger level by env PICOCLAW_LOG_LEVEL

[lanmaoxinqing]

📝 Description

Add support for PICOCLAW_LOG_LEVEL environment variable to allow users to control log level via environment variable, hiding intermediate log outputs such as tool calls during execution.

🗣️ Type of Change

• 🐞 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 📖 Documentation update
• ⚡ Code refactoring (no functional changes, no api changes)

🤖 AI Code Generation

• 🤖 Fully AI-generated (100% AI, 0% Human)
• 🛠️ Mostly AI-generated (AI draft, Human verified/modified)
• 👨‍💻 Mostly Human-written (Human lead, AI assisted or none)

📚 Technical Context (Skip for Docs)

when executing picoclaw agent -m "task", the log output is too verbose, especially for tool call logs. By adding environment variable support, users can set log level to WARN or ERROR to hide INFO-level tool call logs.

🧪 Test Environment

• Hardware: PC
• OS: macOS
• Model/Provider:
• Channels:

📸 Evidence (Optional)

  # Usage
  export PICOCLAW_LOG_LEVEL=WARN
  picoclaw agent -m "your task"

  # Supported log levels (case-insensitive)
  # DEBUG, INFO, WARN, WARNING, ERROR, FATAL

☑️ Checklist

• My code/docs follow the style of this project.
• I have performed a self-review of my own changes.
• I have updated the documentation accordingly.

[CLAassistant]

All committers have signed the CLA.

[yinwm]

⚠️ Compatibility Notice

This PR needs to be checked for compatibility with #1239 (refactor logger to zerolog).

#1239 has been merged to main and introduced significant changes to the logger:

1. init() function completely rewritten - This PR is based on the old implementation
2. Logger struct removed - logger = &Logger{} will cause compilation failure
3. zerolog has built-in ParseLevel() - No need to write a custom parseLevel function

Suggested Changes

func init() {
    once.Do(func() {
        zerolog.SetGlobalLevel(zerolog.InfoLevel)
        consoleWriter := zerolog.ConsoleWriter{
            Out:        os.Stdout,
            TimeFormat: "15:04:05",
        }
        logger = zerolog.New(consoleWriter).With().Timestamp().Logger()
        fileLogger = zerolog.Logger{}
    })

    // Support PICOCLAW_LOG_LEVEL environment variable
    if levelStr := os.Getenv("PICOCLAW_LOG_LEVEL"); levelStr != "" {
        if level, err := zerolog.ParseLevel(levelStr); err == nil {
            SetLevel(level)
        }
    }
}

Please rebase onto the latest main branch and adapt to the zerolog implementation.

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🤖 Detected by Claude Code

[yinwm]

Closing this PR as #1853 (config-based log level setting) has already been merged. The config file approach provides a more comprehensive solution for log level configuration. If you still need environment variable support for CI/CD scenarios, please feel free to reopen or open a new PR discussing the use case.