Take ktfmt's defaults for the Kotlin half

The server half went to rustfmt's defaults earlier today; this is the same
move for the app, and the same reasoning. Kotlin ships no formatter with
the Gradle build, so the question was which to adopt: ktfmt is Kotlin-org
owned now (it moved from facebook/ktfmt), is a formatter rather than a
configurable linter, and has essentially nothing to tune -- which is what
rule 27 is asking for. ktlint's .editorconfig surface is the thing that
rule warns against, and detekt is static analysis, whose job Android Lint
already does here.

One setting, and it is a choice between the tool's own two styles rather
than a tuning: kotlinLangStyle() is the 4-space one, which is what this
code already was. The 2-space default would have reindented every file to
say nothing.

  ./gradlew :androidApp:ktfmtFormat   to apply
  ./gradlew :androidApp:ktfmtCheck    to verify

Formatting only. The one thing worth checking by hand was the generated
PEM constant, since a leading newline there costs Android's
CertificateFactory its preamble sniff and fails at runtime nowhere near
the cause: ktfmt moved `.trimMargin()` onto its own line and left the
template alone, and the regenerated constant still starts at the opening
quotes.

Verified after: ktfmtCheck, compileDebugKotlin and lintDebug all pass, and
the APK builds.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017xn8nHw1tw1R6PtiY1eEtw

app/androidApp/src/main/kotlin/com/example/aiapp/AppRoot.kt

@@ -10,21 +10,24 @@ import androidx.compose.runtime.setValue
 import androidx.compose.ui.platform.LocalContext
 
 /**
- * One `when` rather than a navigation library: four screens, with the list
- * as the root and the back button the only other way between them.
+ * One `when` rather than a navigation library: four screens, with the list as the root and the back
+ * button the only other way between them.
  */
 private sealed class Screen {
     data object SessionList : Screen()
+
     data class Session(val summary: SessionSummary) : Screen()
+
     data object Spawn : Screen()
+
     data object Usage : Screen()
+
     data object Settings : Screen()
 }
 
 /**
- * [settingsVersion] bumps when enrollment lands via an `aiapp://` intent
- * (see MainActivity), re-reading the stored settings -- a plain `remember`
- * would keep serving the pre-enrollment null.
+ * [settingsVersion] bumps when enrollment lands via an `aiapp://` intent (see MainActivity),
+ * re-reading the stored settings -- a plain `remember` would keep serving the pre-enrollment null.
  */
 @Composable
 fun AppRoot(settingsVersion: Int) {
@@ -63,35 +66,39 @@ fun AppRoot(settingsVersion: Int) {
     }
 
     when (val here = screen) {
-        is Screen.SessionList -> SessionListScreen(
-            settings = current,
-            reloadToken = reloadToken,
-            onOpen = { screen = Screen.Session(it) },
-            onSpawn = { screen = Screen.Spawn },
-            onUsage = { screen = Screen.Usage },
-            onSettings = { screen = Screen.Settings },
-        )
-        is Screen.Session -> SessionScreen(
-            settings = current,
-            summary = here.summary,
-            onBack = goToList,
-        )
-        is Screen.Spawn -> SpawnScreen(
-            settings = current,
-            onSpawned = { spawned ->
-                reloadToken++
-                screen = Screen.Session(spawned)
-            },
-            onBack = goToList,
-        )
+        is Screen.SessionList ->
+            SessionListScreen(
+                settings = current,
+                reloadToken = reloadToken,
+                onOpen = { screen = Screen.Session(it) },
+                onSpawn = { screen = Screen.Spawn },
+                onUsage = { screen = Screen.Usage },
+                onSettings = { screen = Screen.Settings },
+            )
+        is Screen.Session ->
+            SessionScreen(
+                settings = current,
+                summary = here.summary,
+                onBack = goToList,
+            )
+        is Screen.Spawn ->
+            SpawnScreen(
+                settings = current,
+                onSpawned = { spawned ->
+                    reloadToken++
+                    screen = Screen.Session(spawned)
+                },
+                onBack = goToList,
+            )
         is Screen.Usage -> UsageScreen(settings = current, onBack = goToList)
-        is Screen.Settings -> SettingsScreen(
-            existing = current,
-            onSaved = { saved ->
-                settings = saved
-                goToList()
-            },
-            onBack = goToList,
-        )
+        is Screen.Settings ->
+            SettingsScreen(
+                existing = current,
+                onSaved = { saved ->
+                    settings = saved
+                    goToList()
+                },
+                onBack = goToList,
+            )
     }
 }