docs(cli): state that os test validates each suite before running it (#6247)

The load-site parse is user-visible behaviour: a suite that does not match
`TestSuiteSchema` is now refused before it runs, named, and counted as one
failed suite while the rest of the glob continues. The `os test` section
listed the flags and said nothing about what happens to a bad file.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Up7rAGwREEy754haLKVtZH

Author: claude

content/docs/deployment/cli.mdx

@@ -1020,6 +1020,12 @@ os test --url http://localhost:4000    # Custom server URL
 os test --token my-api-key            # With authentication
 ```
 
+Each file is validated against `TestSuiteSchema` **before it runs**. A suite that
+does not match is refused at load time, naming the file and every offending path,
+and counts as one failed suite — the rest of the glob still runs. This is what
+stops a malformed suite from reporting success: a misspelled `steps` key used to
+produce a scenario that passed having executed nothing.
+
 #### `os doctor`
 
 Checks your development environment and reports issues: