[FEATURE] Validate endpoints in the cli (#415)

* add validate to cli

* tests

* docs

* linting

* Add summary for running validate

Author: burtenshaw

docs/environment-builder.md

@@ -288,6 +288,35 @@ openenv validate --verbose
 
 `openenv validate` checks for required files, ensures the Dockerfile/server entrypoints function, and lists supported deployment modes. The command exits non-zero if issues are found so you can wire it into CI.
 
+You can also validate a running environment endpoint and get criteria-level JSON:
+
+```bash
+openenv validate --url http://localhost:8000
+# or
+openenv validate https://username-my-env.hf.space
+```
+
+Example runtime output:
+
+```json
+{
+  "target": "http://localhost:8000",
+  "validation_type": "running_environment",
+  "standard_version": "1.0.0",
+  "passed": true,
+  "summary": {
+    "passed_count": 6,
+    "total_count": 6,
+    "failed_criteria": []
+  },
+  "criteria": [
+    {"id": "health_endpoint", "passed": true},
+    {"id": "metadata_endpoint", "passed": true},
+    {"id": "schema_endpoint", "passed": true}
+  ]
+}
+```
+
 ### 8. Push & Share with `openenv push`
 
 Once validation passes, the CLI can deploy directly to Hugging Face Spaces or any registry: