Add examples

[elijahpetty]

The accompanying doc will be in a deephaven-core PR.

[Copilot]

Pull request overview

This PR adds example code demonstrating three Python packaging scenarios for Deephaven applications: a library-only package, a CLI-only package, and a combined package. The examples show how to structure Python packages using modern packaging standards with pyproject.toml, implement CLI tools with Click, and create reusable Deephaven query functions.

Changes:

• Added three complete example packages (my_dh_library, my_dh_cli, my_dh_toolkit) demonstrating different packaging approaches
• Included sample CSV data files for testing the examples
• Updated main README with comprehensive documentation on package structure, usage patterns, and troubleshooting

Reviewed changes

Copilot reviewed 34 out of 38 changed files in this pull request and generated 29 comments.

Show a summary per file

File	Description
my_dh_library/*	Library-only package with reusable Deephaven query and utility functions
my_dh_cli/*	CLI-only package with command-line tools for CSV processing
my_dh_toolkit/*	Combined package with both library functions and CLI tools
data/*	Sample CSV files for testing the example packages
README.md	Comprehensive documentation covering all three packaging scenarios and usage examples

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