fix(02-03): expand expected placeholders after replay capture

Unquoted numeric id placeholders made recorded JSON illegal to parse.
Replay now recaptures, persists vars, expands the expected body, and
diffs against the live response.

Co-authored-by: Cursor <cursoragent@cursor.com>

tide/capture_test.go

@@ -272,6 +272,53 @@ func post(t *testing.T, url, session, ct, body string) {
 	}
 }
 
+func TestReplayExpandsUnquotedIDPlaceholdersAfterCapture(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		switch r.URL.Path {
+		case "/login":
+			_, _ = w.Write([]byte(`{"token":"` + testJWT + `","user":{"id":1}}`))
+		case "/genres":
+			_, _ = w.Write([]byte(`{"data":[{"id":1,"name":"Rock","album_count":0}]}`))
+		default:
+			http.NotFound(w, r)
+		}
+	}))
+	t.Cleanup(srv.Close)
+
+	flow := Flow{
+		Version: 1,
+		Name:    "seed-then-list",
+		Steps: []Step{
+			{
+				ID:      "login",
+				Request: Request{Method: http.MethodPost, Path: "/login"},
+				Response: Response{
+					Status:  200,
+					Headers: jsonCT(),
+					Body:    Body(`{"token":"{{jwt:alice}}","user":{"id":{{id:alice}}}}`),
+				},
+				Capture: []CaptureRule{
+					{From: "response.json", Path: "$.token", As: "jwt:alice", Category: "jwt"},
+					{From: "response.json", Path: "$.user.id", As: "id:alice"},
+				},
+			},
+			{
+				ID:      "genres",
+				Request: Request{Method: http.MethodGet, Path: "/genres"},
+				Response: Response{
+					Status:  200,
+					Headers: jsonCT(),
+					Body:    Body(`{"data":[{"id":{{id:alice}},"name":"Rock","album_count":0}]}`),
+				},
+			},
+		},
+	}
+	if _, err := ReplayFlow(context.Background(), flow, ReplayConfig{Target: srv.URL}); err != nil {
+		t.Fatalf("replay with unquoted id placeholders: %v", err)
+	}
+}
+
 func TestScrubShortNumericIDsDoNotCorruptPaths(t *testing.T) {
 	store, err := OpenStore("")
 	if err != nil {