Add __classdictcell__ to ignored attributes (Python 3.14 support)

[saulshanabrook]

https://egraphs.zulipchat.com/#narrow/channel/375765-egg.2Fegglog/topic/Cost.20function.3A.20using.20function.20values.20of.20subtrees/near/577236488

[saulshanabrook]

@actions-user changelog

[Copilot]

Pull request overview

Updates egglog’s Python class-inspection logic to tolerate a new interpreter-injected attribute in Python 3.14, preventing accidental registration/processing of that attribute.

Changes:

• Add __classdictcell__ to IGNORED_ATTRIBUTES in python/egglog/egraph.py.
• Add an UNRELEASED changelog entry documenting the Python 3.14 compatibility change.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
python/egglog/egraph.py	Ignores the new __classdictcell__ attribute during class namespace inspection to maintain compatibility on Python 3.14.
docs/changelog.md	Documents the change under UNRELEASED.

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[Copilot]

In the changelog entry, __classdictcell__ is written with double-underscores but without code formatting, which Markdown renders as bold/italic in some renderers. Wrap the attribute name in backticks to keep it readable and consistent with other changelog entries (e.g., __call__, Expr.__replace_expr__).

Suggested change

	- Add __classdictcell__ to ignored attributes (Python 3.14 support) [#403](https://github.com/egraphs-good/egglog-python/pull/403)
	- Add `__classdictcell__` to ignored attributes (Python 3.14 support) [#403](https://github.com/egraphs-good/egglog-python/pull/403)