Implement TTD-DR research algorithm and improve query extraction

Added the Test-Time Diffusion Deep Researcher (TTD-DR) algorithm to deep_research/research_engine.py, including draft generation, gap analysis, denoising, self-evolution, and finalization steps. Enhanced extract_search_queries in web_search_plugin.py to allow periods in queries, improving extraction for cases like 'Python 3.12'.

Author: codelion