docs: simplify README and add architecture + comprehensive legacy docs

- Replace verbose marketing README with concise Quick Start, Everyday CLI and LM Studio workflow
- Add interactive architecture assets (docs/architecture/architecture.html + .md)
- Add extensive legacy documentation covering performance, fixes, audits and guides:
  - AGENT-MCP-TOOL-GUIDE.md
  - ALL_PERFORMANCE_OPTIMIZATIONS.md
  - BUG_FIXES_SUMMARY.md
  - CODEGRAPH-MCP-TOOLS-GUIDE.md
  - COMPLETE-LOCAL-SETUP.md
  - CRITICAL_PERFORMANCE_FIXES.md
  - FAQ-TROUBLESHOOTING.md
  - FAST_INSIGHTS_PIPELINE.md
  - IMPROVEMENTS_PHASE2.md
  - MCP_IMPROVEMENTS.md
  - MCP_TOOLS_AUDIT.md
  - MCP_TOOLS_IMPROVEMENTS.md
  - PERFORMANCE_ANALYSIS.md
  - SIMPLIFIED_CONFIG.md

These docs document indexer/mcp improvements (project-relative storage), caching & batching optimizations, FAISS/IVF recommendations, embedding generator batching, tool timeouts/limits, troubleshooting, and migration notes to improve developer onboarding and operational clarity.

Author: jruokola