Skip PEP 440 range specifications during rewrites #10

Summary

Detect Python version ranges such as ^3.12, >=3.12,<3.13, or wildcards that are intentionally non-pinned, and skip mutating them.

Why

The action should avoid rewriting broad specifiers into a hard pin. These ranges show user intent (e.g. keeping compatibility across a track) and forcing a patch update could break workflows or requirements files.

What needs to happen

• Extend discovery to classify PEP 440 range expressions vs. exact pins.
• Ensure range specs are logged in the run summary but reported as skipped with a clear reason.
• Document the behavior so users know when to expect a no-op.
• Add regression tests covering common range syntax in requirements, pyproject, Pipfile, and tox contexts.

References

• Roadmap item: "Skip non-pinned specs" under hardening.
• PEP 440 for accepted version range syntax.

Acceptance criteria

• Ranges remain untouched, while existing pinned detection still works.
• Change matrix and run outputs explain why ranges were skipped.
• README (or docs) include a short note describing the new logic.