Revert to original state + Gateway installer fix

- Revert all IdeFlavor changes back to IC (original working state)
- Only change: Gateway uses installer format instead of non-installer
- Test Gateway fix in isolation to identify root cause

Author: aseemxs

buildSrc/src/main/kotlin/toolkit-intellij-subplugin.gradle.kts

@@ -95,7 +95,7 @@ dependencies {
 
             create(type, version, useInstaller = false)
         } else {
-            create(IntelliJPlatformType.Gateway, version, useInstaller = false)
+            create(IntelliJPlatformType.Gateway, version)
         }
 
         bundledPlugins(toolkitIntelliJ.productProfile().map { it.bundledPlugins })

plugins/amazonq/chat/jetbrains-community/build.gradle.kts

@@ -8,7 +8,7 @@ plugins {
 }
 
 intellijToolkit {
-    ideFlavor.set(IdeFlavor.IU)
+    ideFlavor.set(IdeFlavor.IC)
 }
 
 dependencies {

plugins/amazonq/codetransform/jetbrains-community/build.gradle.kts

@@ -8,7 +8,7 @@ plugins {
 }
 
 intellijToolkit {
-    ideFlavor.set(IdeFlavor.IU)
+    ideFlavor.set(IdeFlavor.IC)
 }
 
 dependencies {

plugins/amazonq/codewhisperer/jetbrains-community/build.gradle.kts

@@ -8,7 +8,7 @@ plugins {
 }
 
 intellijToolkit {
-    ideFlavor.set(IdeFlavor.IU)
+    ideFlavor.set(IdeFlavor.IC)
 }
 
 dependencies {

plugins/amazonq/shared/jetbrains-community/build.gradle.kts

@@ -9,7 +9,7 @@ plugins {
 }
 
 intellijToolkit {
-    ideFlavor.set(IdeFlavor.IU)
+    ideFlavor.set(IdeFlavor.IC)
 }
 
 dependencies {

plugins/core/jetbrains-community/build.gradle.kts

@@ -45,8 +45,7 @@ tasks.compileKotlin {
 }
 
 intellijToolkit {
-    // For 2025.3+, use IU (Ultimate) as the unified platform since IC (Community) was discontinued
-    ideFlavor.set(IdeFlavor.IU)
+    ideFlavor.set(IdeFlavor.IC)
 }
 
 // expose intellij test framework to fixture consumers

plugins/toolkit/jetbrains-core/build.gradle.kts

@@ -28,7 +28,7 @@ plugins {
 }
 
 intellijToolkit {
-    ideFlavor.set(IdeFlavor.IU)
+    ideFlavor.set(IdeFlavor.IC)
 }
 
 dependencies {