Refactor development mode checks to use DEV_UI_ENABLED constant. Updated conditional logic throughout the App component to improve clarity and maintainability. Removed deprecated demo session button to streamline the UI.

src/renderer/App.tsx

@@ -113,7 +113,7 @@ const App = () => {
     setGitCheckInProgress(true);
 
     try {
-      if (IS_DEV && simulateToolsMissingRef.current) {
+      if (DEV_UI_ENABLED && simulateToolsMissingRef.current) {
         const simulated = {
           git: { ok: false, command: "git", error: "simulated_missing" },
           lfs: { ok: false, command: "git lfs", error: "simulated_missing" },
@@ -303,7 +303,7 @@ const App = () => {
 
           if (serverRecoveryActive) {
             setServerRecoveryActive(false);
-            if (IS_DEV) {
+            if (DEV_UI_ENABLED) {
               setDevProceedReady(true);
             } else {
               scheduleScreenTransition("login");
@@ -315,7 +315,7 @@ const App = () => {
             return;
           }
 
-          if (IS_DEV) {
+          if (DEV_UI_ENABLED) {
             setDevProceedReady(true);
             return;
           }
@@ -870,7 +870,9 @@ const App = () => {
                   className="ghost"
                   onClick={() => {
                     setSkipToolsCheck(true);
-                    scheduleScreenTransition(IS_DEV ? "login" : hasSession ? "main" : "login");
+                    scheduleScreenTransition(
+                      DEV_UI_ENABLED ? "login" : hasSession ? "main" : "login"
+                    );
                   }}
                 >
                   나중에 진행
@@ -878,7 +880,7 @@ const App = () => {
               </div>
             </div>
           )}
-          {IS_DEV &&
+          {DEV_UI_ENABLED &&
             serverHealthy &&
             (skipToolsCheck ||
               Boolean(gitCheckResult?.git.ok && gitCheckResult?.lfs.ok)) && (
@@ -894,7 +896,7 @@ const App = () => {
                 다음으로 이동
               </button>
             )}
-          {IS_DEV && (
+          {DEV_UI_ENABLED && (
             <button
               type="button"
               className="ghost"
@@ -950,22 +952,6 @@ const App = () => {
             >
               비밀번호 변경
             </button>
-            <button
-              type="button"
-              className="ghost"
-              onClick={() => {
-                const fallbackId = loginId.trim() || "demo";
-                setProfile({
-                  username: fallbackId,
-                  nickname: "Demo",
-                  level: 1
-                });
-                setHasSession(true);
-                setScreen("main");
-              }}
-            >
-              유효 세션 가정(데모)
-            </button>
           </div>
         </section>
       )}