docs: update cuDNN sliding window attention support

[sbhavani]

Description

Update documentation to reflect that cuDNN now supports causal sliding window attention (SWA) starting from version 9.2+.

Type of change

• Documentation change (change only to the documentation, either a fix or a new content)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Infra/Build change
• Code refactoring

Changes

Please list the changes introduced in this PR:

Changes:

• Updated backend support matrix table to show cuDNN supports SWA (cuDNN 9.2+, causal masks only)
• Added SWA comparison between flash-attention and cuDNN in section 1.3
• Added clarifying note in cp_ag_thd_dpa_jax_deep_dive.ipynb that cuDNN supports SWA but not all striping patterns for context parallelism

Checklist:

• I have read and followed the contributing guidelines
• The functionality is complete
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[greptile-apps]

Greptile Summary

Updated documentation to reflect cuDNN's sliding window attention (SWA) support added in version 9.2+.

Changes Made

• Updated backend support matrix table to show cuDNN supports SWA starting from version 9.2+
• Added detailed SWA comparison between flash-attention and cuDNN in section 1.3, clarifying version-specific support (SWA(left, 0) from cuDNN 9.2, SWA(left, right) from cuDNN 9.6)
• Added note about cuDNN supporting SWA for causal masks only, without dropout, and with bias_type="no_bias"
• Minor formatting improvement in JAX notebook

Review Notes

The documentation changes are accurate and well-aligned with the codebase. Test files confirm cuDNN 9.2.1+ requirement for SWA tests, and code comments validate the causal mask restriction for cuDNN SWA support.

Confidence Score: 5/5

• This PR is safe to merge - documentation-only changes with accurate information
• Perfect score reflects documentation-only changes that accurately describe cuDNN SWA support introduced in version 9.2+, validated against test files and code comments in the repository
• No files require special attention

Important Files Changed

Filename	Overview
docs/examples/attention/attention.ipynb	Updated backend support matrix and added SWA comparison details between flash-attention and cuDNN - accurate documentation changes reflecting cuDNN 9.2+ SWA support
docs/examples/attention/cp_ag_thd_dpa_jax_deep_dive.ipynb	Minor formatting change - added blank line with no functional impact

_{Last reviewed commit: 251e6b2}

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[pggPL]

LGTM

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