docs: add internal docs index

Author: rexleimo

docs/internal/index.md

@@ -0,0 +1,35 @@
+# Internal Docs Index
+
+This folder contains **repository-internal** documentation.
+
+- Do **not** wire anything under `docs/internal/` into `docs-site/` or `mkdocs.yml`.
+- Public docs are built only from `docs-site/`.
+
+## Maintainership quick links
+
+### Boundaries
+
+- [Public docs boundary (what can be published)](public-docs-boundary.md)
+
+### Runtime maps
+
+- [Runtime module map (post-readability refactor)](runtime-module-map.md)
+
+### OKRs
+
+- [2026-03 Readability OKR (zh-CN)](2026-03-readability-okr.zh-CN.md)
+
+### Security (internal)
+
+- [Network + egress security notes](loopforge-network-security.md)
+
+### Plans and references
+
+- [Implementation plans](../plans/)
+- [Competitive archive](competitive/)
+
+## Authoring rules (internal)
+
+- Prefer **dated** filenames for plans/notes: `YYYY-MM-DD-<topic>.md`.
+- Keep “user-path” docs in `docs-site/`; keep maintainer maps, strategy, and competitor notes here.
+- When a doc is bilingual, put the language in the filename (example: `*.zh-CN.md`).