Replace String() calls with .toString()/.toLocaleString() per ast-grep rule

- Add formatError() helper in CLI to safely handle unknown error types
- Add uniqueTestId() helper for generating unique test identifiers
- Replace String(id) with id.toString() for database ID conversions
- Replace String(n) with n.toLocaleString() for user-facing number formatting
- Fix TypeScript errors in test files (undefined checks, unused variables)
- Update lint commands to include ast-grep scanning

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/cli/src/routes/org/add-site.ts

@@ -1,6 +1,7 @@
 import type { LocalContext } from "../../context.js";
 import { buildCommand } from "@stricli/core";
 import { createApiClient } from "../../utils/api-client.js";
+import { formatError } from "../../utils/format-error.js";
 
 interface AddSiteFlags {
   org: string;
@@ -18,10 +19,7 @@ async function addSite(this: LocalContext, flags: AddSiteFlags): Promise<void> {
 
     console.log(`Added site ${flags.domain} to org ${flags.org}`);
   } catch (error) {
-    console.error(
-      "Error:",
-      error instanceof Error ? error.message : String(error),
-    );
+    console.error("Error:", formatError(error));
     this.process.exit(1);
   }
 }