Add justfile with useful commands and bump version to 0.1.6

[Copilot]

This PR adds a comprehensive justfile to streamline development workflows and bumps the project version from 0.1.5 to 0.1.6.

Changes Made

📋 Justfile Commands Added

The new justfile provides the following useful commands for developers:

Build & Run:

• just build - Build in debug mode
• just build-release - Build in release mode
• just run [args] - Run the application with optional arguments
• just build-multi - Multi-platform builds using existing build script

Code Quality:

• just check - Fast error checking
• just clippy - Run linter
• just fmt - Format code
• just fmt-check - Check formatting
• just fix - Auto-fix linting issues

Testing & Development:

• just test - Run tests
• just dev - Development workflow (format + check + test)
• just quick - Quick check (check + clippy)
• just ci - Full CI workflow
• just release - Release workflow (ci + release build)

Utilities:

• just clean - Clean build artifacts
• just install - Install binary to ~/.cargo/bin
• just update - Update dependencies
• just deps - Show dependency tree
• just info - Show project information

🔄 Version Bump

• Updated version from 0.1.5 to 0.1.6 in Cargo.toml
• The version module automatically picks up the new version via CARGO_PKG_VERSION

🧹 Code Cleanup

As part of testing the justfile commands, several linting issues were automatically fixed:

• Removed unused imports
• Applied modern Rust formatting patterns
• Fixed derivable implementations

Usage

After this PR, developers can use simple commands like:

just info          # Show project info
just dev           # Quick development workflow  
just build-release  # Production build
just --list        # See all available commands

This significantly improves the developer experience by providing consistent, discoverable commands for common tasks.

Fixes #1.

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[RobbyV2]

error[E0433]: failed to resolve: use of unresolved module or unlinked crate env
--> src/input/mod.rs:40:37
|
40 | let shell = env::var("SHELL").unwrap_or_default();
| ^^^ use of unresolved module or unlinked crate env
|
= help: if you wanted to use a crate named env, use cargo add env to add it to your Cargo.toml

[Copilot]

error[E0433]: failed to resolve: use of unresolved module or unlinked crate env
--> src/input/mod.rs:40:37
|
...

Fixed the missing std::env import in commit 46e3461. The import was accidentally removed during automatic linting but is needed for the Windows-specific code that checks the SHELL environment variable. The build now passes for both Linux and Windows targets.