Document Tao dialog + CompositionLocal migration notes

Add Step 4 sub-sections covering:
- JewelDecoratedDialog now ships an extension on NucleusApplicationScope
  that's required for the Tao backend.
- Parent CompositionLocals propagate across the Tao ComposeScene boundary,
  so the double IntUiTheme wrap workaround is no longer needed.

Also add matching Troubleshooting entries for the two errors users were
hitting (NoClassDefFoundError on DecoratedDialogKt, No TextStyle provided
on Tao).

Author: kdroidFilter

docs/migration-2.0.md

@@ -272,6 +272,49 @@ The call site (inside `nucleusApplication { … }`) doesn't change — the recei
 
 The plain Compose Desktop `Window` still works inside `nucleusApplication`, but you lose the unified `nucleusWindow` handle and the automatic restore-on-second-instance behavior described below.
 
+### Dialogs follow the same rule
+
+`JewelDecoratedDialog` ships in two flavours, mirroring `JewelDecoratedWindow`:
+
+| Receiver | Backend support |
+|---|---|
+| `JewelDecoratedDialog(…)` (no receiver) | AWT only (JBR / JNI). Crashes on Tao with `NoClassDefFoundError: dev/nucleusframework/window/DecoratedDialogKt`. |
+| `NucleusApplicationScope.JewelDecoratedDialog(…)` | Backend-agnostic. Dispatches to AWT or Tao under the hood. |
+
+Use the scoped variant for anything composed inside `nucleusApplication { … }` — your "About", "Settings", and confirmation dialogs all need it:
+
+```diff
+ @Composable
+-fun MyAboutDialog(onClose: () -> Unit) {
++fun NucleusApplicationScope.MyAboutDialog(onClose: () -> Unit) {
+     JewelDecoratedDialog(onCloseRequest = onClose, title = "About") { … }
+ }
+```
+
+The same applies to `MaterialDecoratedDialog` / the generic `DecoratedDialog` extension on `NucleusApplicationScope`.
+
+### CompositionLocals propagate across the Tao scene boundary
+
+The Tao backend opens a fresh `ComposeScene` per window/dialog. As of 2.0.0-alpha-202605131305 the full parent `CompositionLocalContext` (theme, `LocalDensity`, `LocalLayoutDirection`, user locals, …) is bridged into the new scene automatically — same behavior as Compose's own `Dialog`/`Popup`.
+
+This means you do **not** need to wrap content twice anymore:
+
+```kotlin
+// Before — needed on Tao to avoid "No TextStyle provided" / "No IsDarkTheme provided"
+IntUiTheme(theme, styling) {
+    JewelDecoratedWindow(…) {
+        IntUiTheme(theme, styling) { …content… }   // duplicate
+    }
+}
+
+// After — a single wrap in the parent scope is enough on every backend
+IntUiTheme(theme, styling) {
+    JewelDecoratedWindow(…) { …content… }
+}
+```
+
+If you previously threaded `theme` / `styling` parameters through every custom window or dialog (`JewelOnboardingWindow`, `JewelAboutWindow`, …) to re-apply `IntUiTheme` inside the scene, you can drop the threading: read the theme from the outer scope once.
+
 ---
 
 ## Step 5 — Single Instance Is Automatic
@@ -420,6 +463,12 @@ Pass `enableSingleInstance = false` to `nucleusApplication`. The lock is skipped
 **`Unresolved reference 'JewelDecoratedWindow'` even though the import is correct.**
 The composable became an extension on `NucleusApplicationScope` in 2.0. Wrap-style helper composables must propagate the receiver — see [Step 4](#step-4--replace-window---with-decoratedwindow--).
 
+**`NoClassDefFoundError: dev/nucleusframework/window/DecoratedDialogKt` on the Tao backend.**
+You're calling the AWT-only `JewelDecoratedDialog` (no receiver) under `NucleusBackend.Tao`. Switch the host composable to an extension on `NucleusApplicationScope` so the call resolves to `NucleusApplicationScope.JewelDecoratedDialog`, which dispatches to the right backend — see [Step 4 → Dialogs](#dialogs-follow-the-same-rule).
+
+**`IllegalStateException: No TextStyle provided` / `No IsDarkTheme provided` on Tao but not on AWT.**
+Older Tao builds (pre-`v2.0.0-alpha-202605131225`) did not bridge `CompositionLocals` across the per-window `ComposeScene`. Bump to `2.0.0-alpha-202605131305` or newer and remove any duplicate `IntUiTheme { … }` you added inside the window/dialog content lambda — a single wrap in the outer scope is enough.
+
 **`Could not find org.jetbrains.jewel:jewel-foundation:0.37.…`**
 The IntelliJ snapshots repo is missing. Add `maven("https://www.jetbrains.com/intellij-repository/snapshots")` to `dependencyResolutionManagement.repositories` — see [Prerequisites](#prerequisites).