Emit all supported parameter flags explicitly

Always write both true and false values in the generated
registry so unsupported parameters are visible at a glance
instead of relying on Go zero-value defaults.

Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>

internal/cmd/genmodels/main.go

@@ -193,9 +193,7 @@ func buildSupports(params []string) string {
 		"ResponseFormat", "StructuredOutputs", "Reasoning",
 	}
 	for _, f := range fieldNames {
-		if fields[f] {
-			fmt.Fprintf(&buf, "			%s: true,\n", f)
-		}
+		fmt.Fprintf(&buf, "			%s: %t,\n", f, fields[f])
 	}
 	return buf.String()
 }