test(lint): reduce warning debt in selected test suites

src/tools/builtin/system-info.test.ts

@@ -1,6 +1,13 @@
 import { describe, it, expect } from 'vitest';
 import { systemInfoTool } from './system-info.js';
 
+function getOutput(output: string | undefined): string {
+  if (!output) {
+    throw new Error('Expected output');
+  }
+  return output;
+}
+
 describe('system.info tool', () => {
   // ── Metadata ─────────────────────────────────────────────────────────────
 
@@ -17,14 +24,14 @@ describe('system.info tool', () => {
 
     expect(result.success).toBe(true);
     expect(typeof result.output).toBe('string');
-    expect(result.output!.length).toBeGreaterThan(0);
+    expect(getOutput(result.output).length).toBeGreaterThan(0);
   });
 
   it('output contains expected fields', async () => {
     const result = await systemInfoTool.execute({});
 
     expect(result.success).toBe(true);
-    const output = result.output!;
+    const output = getOutput(result.output);
 
     const expectedFields = [
       'Date:',
@@ -46,17 +53,17 @@ describe('system.info tool', () => {
     const result = await systemInfoTool.execute({});
 
     expect(result.success).toBe(true);
-    const output = result.output!;
+    const output = getOutput(result.output);
 
     // Find the line containing 'ISO 8601:'
     const isoLine = output.split('\n').find((line) => line.includes('ISO 8601:'));
     expect(isoLine).toBeTruthy();
 
     // Extract the ISO string and validate it
-    const isoMatch = isoLine!.match(/ISO 8601:\s*(.+)/);
+    const isoMatch = getOutput(isoLine).match(/ISO 8601:\s*(.+)/);
     expect(isoMatch).toBeTruthy();
 
-    const isoString = isoMatch![1].trim();
+    const isoString = getOutput(isoMatch?.[1]).trim();
     const parsed = new Date(isoString);
     expect(parsed.toISOString()).toBe(isoString);
   });
@@ -78,7 +85,7 @@ describe('system.info tool', () => {
     expect(result2.success).toBe(true);
     expect(typeof result1.output).toBe('string');
     expect(typeof result2.output).toBe('string');
-    expect(result1.output!.length).toBeGreaterThan(0);
-    expect(result2.output!.length).toBeGreaterThan(0);
+    expect(getOutput(result1.output).length).toBeGreaterThan(0);
+    expect(getOutput(result2.output).length).toBeGreaterThan(0);
   });
 });