Prepare v0.3.0 release

[askmy-stack]

Summary

• bump the package version to 0.3.0
• document snapshot provenance and optional comparison artifacts
• update composite Action examples to v0.3.0

Verification

• ...................................................... [100%] (54 passed)
• All checks passed!
• 43 files already formatted
• Success: no issues found in 14 source files
• Successfully built tool_semantics-0.3.0.tar.gz and tool_semantics-0.3.0-py3-none-any.whl

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