Improve error handling and output readability for CLI commands

[ivanvpetrov]

Summary

When certain ig commands are run incorrectly (e.g., missing required sub-commands or arguments),
the CLI currently outputs raw exception stack traces to the user. This is noisy, unhelpful, and
presents a poor developer experience.

Current Behavior

Running ig generate without a sub-command produces output like:

The full yargs internal stack trace is printed in red, even though this is an expected user error
(missing required sub-command), not an unexpected runtime exception.

Expected Behavior

• Known/expected errors (e.g., missing sub-command, invalid arguments) should display a clean,
  actionable message — no stack trace.
• Unexpected runtime errors may still show a stack trace for debugging, but ideally gated behind
  a --verbose or --debug flag.
• Error messages should guide the user toward the correct usage, e.g.:

Error: Please provide a sub-command for "generate".
Usage: ig generate template [name]

Run "ig generate --help" for available options.

Suggested Improvements

• Distinguish between YError (yargs validation errors / expected user mistakes) and actual
  runtime exceptions in the parseAsync callback in cli.ts.
• Suppress stack traces for YError instances.
• Append a usage hint or a pointer to --help when a command is used incorrectly.
• Consider a --verbose flag to opt-in to full stack traces for debugging purposes.

Affected Area

• packages/cli/lib/cli.ts — parseAsync error callback
• packages/cli/lib/commands/generate.ts — demandCommand error message
• Potentially all commands using demandCommand or argument validation