Add YAML AOT spec, update Try .NET spec, and add React page load guide

- Add specs/future/aot-for-yaml.mdx with detailed YamlDotNet AOT migration plan
- Rewrite specs/future/try-dotnet.md: remove shut-down try.dot.net/iframe refs,
  update for Mintlify React component constraints, remove timeframes
- Add flash prevention guide and page mode documentation to Mintlify provider page

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: robertmclaws