⚡ Optimize word count extraction performance

[savvides]

💡 What: Replaced content.split(/\s+/).filter(Boolean).length with (content.match(/\S+/g) || []).length in the word counting logic within extension/content/extractor-core.js and extension/content/extractor.js.
🎯 Why: The previous approach was highly inefficient, as .split allocates a large array for every word and space, and then .filter(Boolean) iterates over it to create yet another array. The new approach directly matches non-whitespace character sequences and returns a single array, bypassing unnecessary allocations and iterations while preserving exactly the same behavior and edge case handling.
📊 Measured Improvement: Benchmarks on large text inputs (100k repetitions of a phrase run 100 times) showed the original method taking ~22.8 seconds versus ~15.9 seconds for the regex match, yielding roughly a ~30% performance boost in execution time and significantly less memory garbage.

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PR created automatically by Jules for task 13257997836342830890 started by @savvides

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