Docs: expand FAQ (#1226)

* Add faq questions

* Fix link in external models concepts page

* Add more faq questions

* Update mkdocs navigation

* Add restatement and forward-only plan questions

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Author: treysp

docs/concepts/models/external_models.md

@@ -25,7 +25,7 @@ FROM
 The following sections demonstrate how to create an external model containing metadata about `external_db.external_table`, which contains columns `column_a` and `column_b`.
 
 ### Using CLI
-Instead of creating the `schema.yaml` file manually, SQLMesh can generate it for you. The [create_external_models](../../../reference/cli#create_external_models) CLI command does exactly this.
+Instead of creating the `schema.yaml` file manually, SQLMesh can generate it for you. The [create_external_models](../../reference/cli.md#create_external_models) CLI command does exactly this.
 
 The command locates all external tables referenced in your SQLMesh project, fetches their schemas (column names and types), and then stores them in the `schema.yaml` file.