docs: reorganize documentation layout

docs/internal/README.md

@@ -0,0 +1,15 @@
+# YAZE Handbook
+
+Internal documentation for planning, AI agents, research, and historical build notes. These
+files are intentionally excluded from the public Doxygen site so they can remain verbose and
+speculative without impacting the published docs.
+
+## Sections
+- `agents/` – z3ed and AI agent playbooks, command abstractions, and debugging guides.
+- `blueprints/` – architectural proposals, refactors, and technical deep dives.
+- `roadmaps/` – sequencing, feature parity analysis, and postmortems.
+- `research/` – emulator investigations, timing analyses, web ideas, and development trackers.
+- `legacy/` – superseded build guides and other historical docs kept for reference.
+
+When adding new internal docs, place them under the appropriate subdirectory here instead of
+`docs/`.