NEW: cascade.diagnostics module
- BugDetector: Static analysis for Python code
- CodeTracer: Runtime execution tracing with causation chains
- ExecutionMonitor: Live monitoring with anomaly detection
- DiagnosticEngine: Unified reporting with markdown output

Bug patterns detected:
- Division by zero, null pointer access, infinite loops (Critical)
- Bare except, resource leaks, race conditions (High)
- Unused variables, dead code, type mismatches (Medium)
- Style issues, naming conventions (Low)

Usage:
  from cascade.diagnostics import diagnose, BugDetector
  report = diagnose('path/to/code.py')
  issues = BugDetector().scan_directory('./project')

Also: Updated README with diagnostics docs, keywords in pyproject.toml