Add async third-party vetting

Queue vetting on third_parties with PENDING, PROCESSING,
COMPLETED, and FAILED states. Expose enqueue and status through
GraphQL, MCP, CLI, and n8n, validate vet requests, tune the
worker via config, and poll the detail page while vetting runs.

Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>

pkg/agent/tool_test.go

@@ -356,7 +356,7 @@ func TestFunctionTool_Execute(t *testing.T) {
 	)
 
 	t.Run(
-		"optional fields can be omitted",
+		"optional fields may be empty but must be present",
 		func(t *testing.T) {
 			t.Parallel()
 
@@ -373,7 +373,7 @@ func TestFunctionTool_Execute(t *testing.T) {
 				},
 			)
 
-			result, err := tool.Execute(context.Background(), `{"city":"Paris"}`)
+			result, err := tool.Execute(context.Background(), `{"city":"Paris","units":""}`)
 			require.NoError(t, err)
 			assert.False(t, result.IsError)
 			assert.Equal(t, "sunny in Paris", result.Content)