Improve moprh exact node matching with scan ahead

[MichaelWest22]

Description

Improve morph exact node matching with scan ahead

Rewrote __findBestMatch to use isEqualNode() for better matching of non-ID nodes during morphing.

Key changes:

• Scan ahead using isEqualNode() to find exact matches for elements without IDs
• Added htmx.config.morphScanLimit (default: 10) to control how many siblings to scan
• ID-based matches always continue scanning regardless of limit
• Stop scanning early when limit is exhausted for non-ID elements (nodeMatchCount === 0)
• Improved sibling duplicate detection to return null when duplicates found
• Renamed siblingSoftMatchCount to siblingMatchCount

This significantly improves morphing accuracy for lists of similar elements without IDs, while maintaining performance through configurable scan limits.

Corresponding issue:

Testing

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Checklist

• I have read the contribution guidelines
• I have targeted this PR against the correct branch (master for website changes, dev for
  source changes)
• This is either a bugfix, a documentation update, or a new feature that has been explicitly
  approved via an issue
• I ran the test suite locally (npm run test) and verified that it succeeded