Extract magic number to named constant in conversion tracking delay

[Copilot]

Addresses review feedback from PR #325 to replace the hardcoded 150ms timeout with a named constant for improved code clarity.

Changes:

• Extracted 150 magic number to CONVERSION_DATA_WAIT_MS constant at function scope
• Added descriptive comment explaining the delay ensures conversion data is set by the conversion extension
• Updated setTimeout call to reference the constant

Before:

}, 150); // Small delay to ensure k5aMeta.conversion is set

After:

// Configuration: delay to ensure conversion data is set by conversion extension
var CONVERSION_DATA_WAIT_MS = 150;

// ... later in code ...
}, CONVERSION_DATA_WAIT_MS);

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