docs: add stream naming convention to topic-suffixes reference

Author: cablehead

docs/src/content/docs/reference/topic-suffixes.mdx

@@ -9,6 +9,20 @@ import { Link } from '../../../utils/links';
 
 cross.stream uses special topic suffixes to coordinate between components and track their lifecycle. This reference documents all suffixes, organized by component type.
 
+## Stream Naming Convention
+
+When creating streams, **use hyphens (`-`) instead of dots (`.`)** in stream names:
+
+```nushell
+# Good - uses hyphens
+"my-stream" | .append
+
+# Avoid - dots can collide with system suffixes
+"my.stream" | .append
+```
+
+Dots are reserved for the suffix convention (e.g., `.spawn`, `.recv`, `.register`). Using dots in stream names could accidentally collide with system topic suffixes, leading to unexpected behavior.
+
 ## Generators
 
 <table>