⚡ Bolt: [Refactor HTML string concatenation to list append in calltree_analysis.py]

[WarGloom]

💡 What: Replaced string concatenations using += with list accumulation (list.append and "".join(list)) for building the complete HTML string in calltree_analysis.py.
🎯 Why: Repetitive string concatenation using += in Python creates significant O(N^2) memory reallocation bottlenecks, especially when dealing with large HTML strings. This is a known issue for large fuzz introspector calltrees. While the immediate subsequent BeautifulSoup parsing dominates the total execution time, building the initial HTML document via standard Python best practices (.append and "".join()) establishes a safer baseline and slightly reduces the localized memory overhead during string construction.
📊 Impact: Standardizes HTML string assembly using optimal Python patterns and reduces memory reallocation during string construction in calltree_analysis.py.
🔬 Measurement: Code review visually confirms the optimization. Profiling the HTML string generation phase (prior to parsing) shows reduced overhead.

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PR created automatically by Jules for task 6719935966594913169 started by @WarGloom

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