docs: document template name format

docs/template/names.mdx

@@ -38,6 +38,17 @@
 
 </CodeGroup>
 
+## Name format
+
+Before a name is used, it's trimmed of surrounding whitespace and lowercased. The result must match the pattern `^[a-z0-9-_]+$`:
+
+- Lowercase letters (`a`–`z`), numbers (`0`–`9`), dashes (`-`), and underscores (`_`)
+- At least one character
+- Leading and trailing dashes or underscores are allowed
+- No maximum length
+
+Uppercase letters are accepted on input and lowercased automatically, so `My-Template` and `my-template` refer to the same name. Any other character (spaces inside the name, dots, slashes, and so on) is rejected.
+
 ## Team-local naming
 
 Template names are scoped to your team. This means:
@@ -45,10 +56,10 @@
 - Your template named `my-app` is stored as `your-team-slug/my-app`
 - You can reference it simply as `my-app` within your team
 - Other teams can have their own `my-app` template without conflict
 - Public templates should be referenced using the full namespaced format (`team-slug/template-name`)
 
 <Info>
 **Backwards Compatibility**: Existing public templates remain accessible without the team slug prefix. New public templates should be referenced using the full namespaced format (`team-slug/template-name`).
 </Info>
 
 ## Common use cases