SGen null-handling parity, micro-opt CV, doc & bench fixes
- Fix SGen collection/dictionary null-handling: always emit PropertySkip for nulls, preventing NREs regardless of nullable annotation.
- Add micro-opt CV threshold (1.5%) to benchmark output for finer-grained result flagging; update reporting and context.
- Benchmark loop: add inter-sample settle delay, trimmed median, and branchless progress for more reliable measurements.
- Add regression tests for SGen null-handling (complex, collection, dictionary; null/non-null; SGen/reflection; FastMode/Default).
- Update docs: clarify SGen null-check contract, add AQN binder security plan, and cross-reference related issues.
- Misc: code cleanups, improved comments, and minor doc clarifications.
Loretta
d4e4c4480a