0.9.1

Reorganize codebase with modular utilities for better maintainability

• Extract trace/logging utilities to $.trace.mjs
• Extract shell detection to $.shell.mjs
• Extract stream utilities to $.stream-utils.mjs and $.stream-emitter.mjs
• Extract shell quoting to $.quote.mjs
• Extract result creation to $.result.mjs
• Extract ANSI utilities to $.ansi.mjs
• Extract global state management to $.state.mjs
• Extract shell settings to $.shell-settings.mjs
• Extract virtual command registration to $.virtual-commands.mjs
• Add commands/index.mjs for module exports
• Update $.utils.mjs to use shared trace module

All new modules follow the 1500-line limit guideline. The Rust code
structure already follows best practices with tests in separate files.

Related Pull Request: #150

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