feat(coderd): add has_external_agent flag to template_versions and workspace_builds (#19285)

This pull request introduces support for external workspace management, allowing users to register and manage workspaces that are provisioned and managed outside of the Coder.

* Added has_external_agent field to workspace builds and template versions

coderd/database/queries/workspacebuilds.sql

@@ -145,15 +145,6 @@ SET
 	updated_at = @updated_at::timestamptz
 WHERE id = @id::uuid;
 
--- name: UpdateWorkspaceBuildAITaskByID :exec
-UPDATE
-	workspace_builds
-SET
-	has_ai_task = @has_ai_task,
-	ai_task_sidebar_app_id = @sidebar_app_id,
-	updated_at = @updated_at::timestamptz
-WHERE id = @id::uuid;
-
 -- name: GetActiveWorkspaceBuildsByTemplateID :many
 SELECT wb.*
 FROM (
@@ -247,3 +238,13 @@ WHERE
 	AND pj.job_status = 'failed'
 ORDER BY
 	tv.name ASC, wb.build_number DESC;
+
+-- name: UpdateWorkspaceBuildFlagsByID :exec
+UPDATE
+	workspace_builds
+SET
+	has_ai_task = @has_ai_task,
+	ai_task_sidebar_app_id = @sidebar_app_id,
+	has_external_agent = @has_external_agent,
+	updated_at = @updated_at::timestamptz
+WHERE id = @id::uuid;