Deprecating Docs.delete's name arg

[jamesbraza]

This PR:

• Starts a deprecation of Docs.delete's name arg
• Denies a silent failure where docname gets ignored if one also specified a different name
• Adds test coverage of Docs.delete

[dosubot]

Documentation Updates

Checked 1 published document(s). No updates required.

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[Copilot]

Pull Request Overview

Deprecates the Docs.delete name argument in favor of docname and adds lifecycle test coverage including document deletion.

• Adds a deprecation warning when the legacy name parameter is used.
• Expands test_docs_lifecycle to assert add returns a docname and to exercise deletion by docname.

Reviewed Changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 3 comments.

File	Description
tests/test_paperqa.py	Adds lifecycle assertions and a new deletion subtest using docname to prepare for deprecation of name.
src/paperqa/docs.py	Introduces deprecation warning logic for the name parameter in delete, preferring docname.

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