Add passthrough arguments to PHP binary via -- separator

[Copilot]

Implementation Plan: Passthrough Arguments via --

• Explore repository structure and understand current implementation
• Modify Server_Command.php to capture and handle passthrough arguments after --
• Update command documentation with the new passthrough feature
• Add Behat tests to verify passthrough arguments work correctly
• Address review feedback:
  • Update test to actually verify the passthrough arg was applied (outputs memory_limit value)
  • Remove dead code (-- check in loop), simplify with str_repeat + array_merge
  • Add @param annotations for $args and $assoc_args

Original prompt

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This section details on the original issue you should resolve

<issue_title>Passthrough args via --?</issue_title>
<issue_description>## Feature Request

• Yes, I reviewed the contribution guidelines.

Describe your use case and the problem you are facing

I want to load Xdebug module into the web server via php -S -dzend_extension=xdebug.so.

Describe the solution you'd like

wp server could pass through additional arguments to php after -- argument.

Example: wp server --docroot=public -- -dzend_extension=xdebug.so

Doing this via wp server --config argument is problematic, because I want to define universally usable commands centrally in composer.json scripts. Due to variety of INI configuration file locations on user's system, which we actually don't want to replace, this doesn't seem to be achievable with a single --config argument.</issue_description>

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

@schlessera Sounds like a reasonable use case.

• Fixes Passthrough args via --? #59

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 15 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/Server_Command.php	0.00%	15 Missing ⚠️

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