Config refactor + stdout output mode

[akx]

This PR:

• upgrades bits and pieces as usual
• refactors things so configuration is read once from env
• adds a no-restart mode, useful for development
• adds a mode where output is JSON(L) written to stdout, for easier plugging into other use cases!

[Copilot]

Pull Request Overview

This PR refactors environment variable handling into a proper configuration system and adds support for writing stats to stdout instead of files only. The refactor centralizes configuration management while maintaining backward compatibility with existing environment variables.

• Replaces direct environment variable access with a centralized Config struct
• Adds stdout output mode as an alternative to file-based stats storage
• Updates all CPU usage functions to accept configurable sample intervals

Reviewed Changes

Copilot reviewed 23 out of 24 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/config.rs	New configuration module with Config struct and centralized env var parsing
src/consts.rs	New constants module extracting shared values from env module
src/store.rs	Refactored to support multiple output modes (file vs stdout) via config
src/main.rs	Updated to use new config system and improved restart logic
src/lib.rs	Modified to accept config parameter and pass it through
src/stats/	Updated CPU usage functions to accept configurable sample intervals
src/env.rs	Removed unused constants moved to consts.rs
README.md	Updated documentation to reflect new output modes and configuration options
Cargo.toml	Updated dependencies including anyhow for error handling

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[ruksi]

good changes all around!

could've used the stdout and no-restart modes when developing 😆