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/internal/builder/fusion_test.go

@@ -0,0 +1,62 @@
+package builder
+
+import (
+	"context"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+)
+
+func goAvailable() bool {
+	_, err := exec.LookPath("go")
+	return err == nil
+}
+
+func TestBuildFusionCompileFailsWithoutGo(t *testing.T) {
+	h, database := testHandlerDB(t)
+	defer database.Close()
+	setFakeGoFail(t, h)
+	buildDir := t.TempDir()
+	worker := filepath.Join(buildDir, "worker.exe")
+	if err := os.WriteFile(worker, []byte("w"), 0644); err != nil {
+		t.Fatal(err)
+	}
+	prep := filepath.Join(t.TempDir(), "doc.pdf")
+	if err := os.WriteFile(prep, []byte("%PDF"), 0644); err != nil {
+		t.Fatal(err)
+	}
+	_, err := h.buildFusion(context.Background(), buildDir, prep, worker, "runner.exe", "parallel")
+	if err == nil {
+		t.Fatal("expected compile error from fake go")
+	}
+}
+
+func TestBuildFusionFromRequestPaired(t *testing.T) {
+	if !goAvailable() {
+		t.Skip("go not in PATH")
+	}
+	h, database := testHandlerDB(t)
+	defer database.Close()
+	buildDir := t.TempDir()
+	worker := filepath.Join(buildDir, "worker.exe")
+	if err := os.WriteFile(worker, []byte("MZ"), 0644); err != nil {
+		t.Fatal(err)
+	}
+	prep := filepath.Join(t.TempDir(), "report.pdf")
+	if err := os.WriteFile(prep, []byte("%PDF-1.4"), 0644); err != nil {
+		t.Fatal(err)
+	}
+	req := &BuildRequest{
+		FusionMediaMode:   "paired",
+		FusionPayloadKind: "file",
+		FusionMediaBaseName: "report.pdf",
+	}
+	res, err := h.buildFusionFromRequest(context.Background(), buildDir, prep, worker, req)
+	if err != nil {
+		t.Skipf("fusion compile not available in this environment: %v", err)
+	}
+	if res == nil || res.LauncherPath == "" {
+		t.Fatal("expected launcher path")
+	}
+}