Add --skip-duplicates flag to wp media import

[Copilot]

• Add --skip-duplicates flag to import() docblock and @param type hint
• Add $skips = 0 variable in import()
• Add duplicate detection for local files using _wp_attached_file basename match
• Add duplicate detection for remote files using _wp_attached_file basename match (extracted from URL)
• Use RIGHT(meta_value, N) = '/basename' query to match year/month subdirectory paths without % wildcards
• Use mb_strlen() with strlen() fallback for correct character counting
• Use explode() instead of strtok() consistently for URL query-string stripping
• Pass $skips to report_batch_operation_results only when --skip-duplicates is active
• Add find_duplicate_attachment() private helper method
• Fix duplicate detection for WP 5.3+ scaled images: derive basename-scaled.ext from the input basename and include it in the _wp_attached_file search — WordPress stores the scaled variant name in _wp_attached_file, not as a separate meta key
• Add Behat test scenarios for --skip-duplicates (local file, remote file, mixed batch)
• Fix CI failures: local file skip test and mixed-batch skip test were failing because large-image.jpg is large enough to trigger WP scaling

Original prompt

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This section details on the original issue you should resolve

<issue_title>Skip Duplicates</issue_title>
<issue_description>## Feature Request

• [X ] Yes, I reviewed the contribution guidelines.

Describe your use case and the problem you are facing

I have a directory that I regularly update with images, audio, video, and documents. I want to run wp media import on this directory but have it skip any files that have already been imported. I can't think of a way to do this today other than some complicated scripting on my side that would compare file names and date modified between the two systems.

Describe the solution you'd like

I would love a flag that I could run as part of the command that could automatically do this for me. I plan on setting up a batch job to continuously import from the directory, it would be great if I could just run wp media import --skip_existing or something along those lines.
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Skip Duplicates #152

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[codecov]

Codecov Report

❌ Patch coverage is 95.34884% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/Media_Command.php	95.34%	2 Missing ⚠️

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