Add tag version validation against main branch in CI

[Copilot]

Prevents creating tags that don't increment from the current main branch version. Without this check, tags could be created with versions equal to or lower than main, causing release confusion.

Changes

• New workflow step: Extracts version from fastkml/about.py on main branch and compares against tag being pushed
• Version parsing: Uses packaging.version.parse() to properly handle pre-releases, dev versions, and semantic versioning
• Security: Environment variables prevent shell injection from malicious tag names
• Error handling: Validates version extraction and catches InvalidVersion with clear error messages

Example Behavior

# On main: __version__ = "1.3.0"
# Pushing tag 1.4.0 → ✓ passes
# Pushing tag 1.3.0 → ✗ fails (not greater than main)
# Pushing tag 1.2.0 → ✗ fails (not greater than main)

Runs only when tags are pushed, positioned after the existing tag name validation step.

Original prompt

Compare this tag to the latest version on main

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[semanticdiff-com]

Review changes with  

Changed Files

File	Status
.github/workflows/run-all-tests.yml	0% smaller

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