Expand test coverage across server, agent, and web; fix bugs found during audit.

Adds hundreds of unit/integration/e2e tests, fixes WS bcrypt auth, config merge, fleet analytics, agent schedule/log tail, and documents stale PROBLEMS items. Updates PROBLEMS.md, README, and test scripts; ignores local spread-kits and coverage dirs.

server/web/src/api/client.test.ts

@@ -153,6 +153,12 @@ describe('api client', () => {
     expectAuthHeaders(init);
   });
 
+  it('estimateFusion rejects without prep file', async () => {
+    const req = { fusion_enabled: true } as Parameters<typeof api.estimateFusion>[0];
+    await expect(api.estimateFusion(req, null)).rejects.toThrow('Fusion requires prep.exe upload');
+    expect(fetchMock).not.toHaveBeenCalled();
+  });
+
   it('pinBuild, unpinAll, deleteBuild use correct methods and paths', async () => {
     fetchMock
       .mockResolvedValueOnce(jsonResponse({ ok: true, pinned_id: 'b1' }))