test: add coverage for lastUsedCase partial update and strict schema rejection

Tests that partial PUT /api/settings with just lastUsedCase works correctly
and that including modelConfig triggers strict Zod schema rejection (the bug
fixed in #49).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Ark0N

CLAUDE.md

@@ -6,7 +6,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 | Task | Command |
 |------|---------|
-| Dev server | `npx tsx src/index.ts web` |
+| Dev server | `npm run dev` (or `npx tsx src/index.ts web`) |
 | Type check | `tsc --noEmit` |
 | Lint | `npm run lint` (fix: `npm run lint:fix`) |
 | Format | `npm run format` (check: `npm run format:check`) |
@@ -78,7 +78,7 @@ Codeman is a Claude Code session manager with web interface and autonomous Ralph
 | Production start | `npm run start` |
 | Production logs | `journalctl --user -u codeman-web -f` |
 
-**CI**: `.github/workflows/ci.yml` runs `typecheck`, `lint`, `format:check` on push to master (Node 22). Tests excluded (they spawn tmux).
+**CI**: `.github/workflows/ci.yml` runs `typecheck`, `lint`, `format:check` on push to master/main and on PRs (Node 22). Tests excluded (they spawn tmux).
 
 **Code style**: Prettier (`singleQuote: true`, `printWidth: 120`, `trailingComma: "es5"`). ESLint flat config (`eslint.config.js`) allows `no-console`, warns on `@typescript-eslint/no-explicit-any`. Ignores: `app.js`, `scripts/**/*.mjs`, `src/web/public/vendor/**`, `tools/**`, `remotion/**`.
 

test/routes/system-routes.test.ts

@@ -366,6 +366,36 @@ describe('system-routes', () => {
       expect(body.success).toBe(false);
     });
 
+    it('saves lastUsedCase as partial update without overwriting other settings', async () => {
+      mockedReadFile.mockResolvedValue(
+        JSON.stringify({ showCost: true, showTokenCount: false, subagentTrackingEnabled: true }) as never
+      );
+
+      const res = await harness.app.inject({
+        method: 'PUT',
+        url: '/api/settings',
+        payload: { lastUsedCase: 'my-test-case' },
+      });
+      expect(res.statusCode).toBe(200);
+      expect(JSON.parse(res.body).success).toBe(true);
+
+      const writtenContent = JSON.parse(mockedWriteFile.mock.calls[0][1] as string);
+      expect(writtenContent.lastUsedCase).toBe('my-test-case');
+      expect(writtenContent.showCost).toBe(true);
+      expect(writtenContent.showTokenCount).toBe(false);
+      expect(writtenContent.subagentTrackingEnabled).toBe(true);
+    });
+
+    it('rejects settings with modelConfig (strict schema prevents full-object PUT)', async () => {
+      const res = await harness.app.inject({
+        method: 'PUT',
+        url: '/api/settings',
+        payload: { lastUsedCase: 'test', modelConfig: { model: 'something' } },
+      });
+      // Fastify rejects unknown fields at schema validation level (400) before handler runs
+      expect(res.statusCode).toBe(400);
+    });
+
     it('rejects non-object body', async () => {
       const res = await harness.app.inject({
         method: 'PUT',