fix(vtexplain): case-sensitive COMMENT check for sequence tables

[anujagrawal380]

Description

Fixes a bug where vtexplain fails to recognize vitess_sequence tables when the DDL uses uppercase COMMENT (e.g., COMMENT 'vitess_sequence').

The AST parser preserves the original casing of table options, but the check in vtexplain used a case-sensitive comparison (option.Name == "comment"). Changed to strings.EqualFold so any casing works.

Changes

• Use strings.EqualFold for the comment option name check in vtexplain_vttablet.go
• Added a test case with uppercase COMMENT to verify the fix

Related Issue(s)

Fixes #14941

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

Deployment Notes

AI Disclosure

Tests written by Claude.

[vitess-bot]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.65%. Comparing base (70c7a72) to head (eccb465).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #19444      +/-   ##
==========================================
- Coverage   69.67%   69.65%   -0.02%     
==========================================
  Files        1614     1614              
  Lines      216793   216819      +26     
==========================================
- Hits       151044   151030      -14     
- Misses      65749    65789      +40     

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[anujagrawal380]

PTAL @mattlord