Take REPO_REFACT.md and ECOSYSTEM_PLAN.md under version control

Both were written into the workspace root, which is not a git repo, so
they were versioned nowhere: one `rm` and they were gone, and nobody
else on the team could see them. They belong next to WIKI_CONNECTION.md
— all three describe the estate rather than any single repo.

The references in the ttg-ops skills follow in the marketplace repo.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

README.md

@@ -69,5 +69,17 @@ TTG/
 └── tools_libs/     # own libraries (inkwell, rubbs, gorpg)
 ```
 
-The mapping between repos and wiki pages is described in
-[WIKI_CONNECTION.md](WIKI_CONNECTION.md).
+## Estate documentation
+
+These describe the estate as a whole, which is why they live here rather than in
+any single repo:
+
+- **[WIKI_CONNECTION.md](WIKI_CONNECTION.md)** — which repo is documented by
+  which wiki page, and which Gitea org each repo belongs to.
+- **[REPO_REFACT.md](REPO_REFACT.md)** — the Gitea org structure: what each org
+  is for and what it contains.
+- **[ECOSYSTEM_PLAN.md](ECOSYSTEM_PLAN.md)** — what we have per org towards a
+  complete game development lifecycle, and what is still missing.
+
+The `ttg-ops` plugin in `ttg-marketplace` reads these rather than carrying its
+own copy of the rules.