Update zed validate docs

Author: tstirrat15

pages/spicedb/modeling/validation-testing-debugging.mdx

@@ -164,19 +164,68 @@ Request tracing information by setting `with_tracing: true` in the request messa
 
 ### Zed Validate
 
-Files exported from the [Playground](#playground) can also be validated by the `zed validate` command.
-This is particularly useful for testing locally or checking into a CI/CD workflow.
-If you're using GitHub, there's [GitHub Action][validate-action] for running this validation.
+The `zed` binary provides a means of validating and testing a schema locally and in CI:
 
-[validate-action]: #authzedaction-spicedb-validate
+```sh
+zed validate my-schema.zed
+```
+
+It will load and validate the schema using the same parsing logic that the SpiceDB binary uses,
+ensuring that a schema that passes validation will be considered a valid schema by your SpiceDB instance.
+
+<Callout type="warning">
+Note that a schema write can still fail if a relation is removed and there are still instances of that
+relation in your database. `zed` doesn't know about your data.
+</Callout>
 
-Here's an example using `zed validate`:
+You can validate the functionality of your schema using validation yaml files, such as those exported
+by the [Playground](#playground):
 
+```sh
+zed validate schema-and-validations.yaml
 ```
-$ zed validate schema-and-assertions.yaml
-Success! - 3 relationships loaded, 4 assertions run, 2 expected relations validated
+
+Validation files take this form:
+
+```yaml
+schema: >-
+  // schema goes here
+# -- OR --
+schemaFile: "./path/to/schema.zed"
+
+# Note that relations are a single heredoc string rather than a yaml list
+relationships: >-
+  object:foo#relation@subject:bar
+  object:baz#relation@subject:qux
+
+assertions:
+  assertTrue:
+    - object:foo#relation@subject:bar
+  assertFalse:
+    - object:foo#relation@subject:qux
+validation:
+  object:foo#relation:
+    - "[subject:bar] is <object:foo#user>"
 ```
 
+As of version v0.25.0, `zed validate` command can take multiple files as arguments:
+
+```
+zed validate some-validations.yaml some-other-validations.yaml
+```
+
+This means you can validate a folder full of files using shell globbing:
+
+```
+zed validate validations/*
+```
+
+There's an example of this available in the [examples repository](https://github.com/authzed/examples/tree/main/schemas/multiple-validation-files).
+
+If you're using GitHub, there's a [GitHub Action][validate-action] for running this validation.
+
+[validate-action]: #authzedaction-spicedb-validate
+
 ### Explain Flag
 
 The `zed permission check` command has an optional flag, `--explain`, that will cause SpiceDB to collect the actual paths taken against the live system to compute a permission check.