docs: generate gitea wiki pages + publish script

add wiki/ markdown pages (Home, Sidebar, architecture, transport, developer, usage)

add scripts/publish_gitea_wiki.sh to sync wiki repo

fix: serialize aggregate env-setting tests to avoid parallel env var races

wiki/_Sidebar.md

@@ -0,0 +1,13 @@
+# Navigation
+
+- [[Home]]
+- Architecture
+  - [[Architecture-Overview]]
+  - [[Transport-Contracts]]
+- Developer
+  - [[Developer-Setup]]
+  - [[Testing]]
+- Usage
+  - [[Quick-Start]]
+  - [[API-Examples]]
+  - [[NATS-Reference]]