Refactor docs: topic folders, TOON, XCUT, protocol sync
- Migrated all topic documentation into dedicated folders with canonical `README.md`, `ISSUES.md`, and `TODO.md` per topic (e.g., `LOGGING/`, `SIGNALR/`, `BINARY/`, `TOON/`).
- Added comprehensive TOON serializer documentation: design, format, options, attributes, inference, issues, and TODOs.
- Introduced `XCUT` folder for cross-cutting issues and TODOs, with canonical entries and topic cross-references.
- Updated all references and navigation to use new folder-based doc paths; fixed links and clarified doc structure.
- Enhanced AI agent protocol: enforce session skill preloading, `[LOADED_DOCS: ...]` short-name prefix, and mandatory `docs-check` skill for doc/code sync.
- Updated `.csproj` to include all `README.md` files for IDE visibility.
- Improved and clarified SignalR, grid, and project-level documentation.
- Minor code/test tweaks and doc content corrections for consistency.
Update protocol, docs-discovery skill, and doc layering
- Switched AI AGENT CORE PROTOCOL to new `[LOADED_DOCS: N files (+K this turn: ...)]` prefix format in all primary instruction files; updated examples and enforcement details.
- Added `docs-discovery` skill for proactive .md doc loading before code search; documented usage and integration as a shared agent skill.
- Introduced `## Protocol History` section and `LLM_PROTOCOL_DECISIONS.md` decision log for cross-repo protocol change tracking.
- Expanded protocol-audit skill and `REPOS.md` to support 8 instruction files (primary/inherit split), new invariants, and known issues.
- Added/updated structured TODO and issues docs for serialization, logging, and SignalR binary protocol.
- Improved cross-references, doc layering, and clarified documentation-first coding workflow.
- Various minor doc clarifications and formatting for protocol consistency.
Loretta