app: fixture-mode session screen and a "Run benchmark" control

BenchFixture.kt/BenchNetwork.kt fake the backend for the bench build: a
URLStreamHandlerFactory installed only under BuildConfig.FIXTURE_MODE
answers TranscriptSource/EventStream's requests from an in-memory copy of
the bundled fixture instead of opening a socket, so the fold, the paging
and uniqueItems under test are the screen's real ones rather than a
shortcut built for this. MainActivity opens straight onto that session
when FIXTURE_MODE is set, with no enrollment and no permission prompts.

BenchRun.kt drives the same scroll loop and streaming phase
transcript-bench.sh/stream-bench.sh drive over ui-trace, but in-process
(24 swipes through the real LazyListState, then 400 fixture events
appended at 20/s through the real live-fold path), and adds process CPU
time, peak RSS and battery current to the render report -- "unavailable"
rather than a fabricated number where the device can't answer.

"Run benchmark" sits beside the existing "Copy" in session settings,
found by that exact label the way every other control here is
(SessionSettingsDialog's onRunBenchmark, null on every build but bench).
debugReport gained an optional `extra` section for this; empty and
invisible on every other build's report.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

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

@@ -66,6 +66,35 @@ class MainActivity : ComponentActivity() {
         // Transparent status bar on every version; the Surface below paints through underneath it
         // and content insets itself. Same reasoning as dev-updater's MainActivity.
         enableEdgeToEdge()
+
+        // The `bench` build's entire purpose (P0, docs/RUST.md): open straight onto the session
+        // screen against BenchFixture's in-process fake backend, with no enrollment, no network
+        // permission, and no notification prompt -- none of them mean anything with no server and
+        // no real device to notify. See BenchFixture.kt and BenchNetwork.kt for how a screen built
+        // to talk to a real backend is made to talk to this instead. Still needs the same
+        // status/navigation-bar padding the ordinary flow below applies: edge-to-edge is the
+        // platform's own default from Android 15 on this app's targetSdk, with or without the call
+        // above, so skipping the padding here put the header's own buttons under the status bar --
+        // there to look at, but not there for `ui-trace`'s tap-by-label to land on.
+        if (BuildConfig.FIXTURE_MODE) {
+            installFixtureNetworkOnce()
+            BenchFixture.ensureLoaded(this)
+            setContent {
+                MaterialTheme(colorScheme = AiAppColors) {
+                    Surface(modifier = Modifier.fillMaxSize()) {
+                        Box(Modifier.fillMaxSize().statusBarsPadding().navigationBarsPadding()) {
+                            SessionScreen(
+                                settings = BenchFixture.settings,
+                                summary = benchSessionSummary(),
+                                onBack = { finish() },
+                                onFiles = {},
+                            )
+                        }
+                    }
+                }
+            }
+            return
+        }
         // Dark status-bar icons only over a light background, decided from the scheme rather than
         // fixed. It was hardcoded to `true`, which was right against the default light surface and
         // became unreadable the moment the app wore Catppuccin Mocha.
@@ -147,6 +176,26 @@ class MainActivity : ComponentActivity() {
         }
     }
 
+    /** The one session the `bench` build ever shows -- BenchFixture's session id, nothing else. */
+    private fun benchSessionSummary() =
+        SessionSummary(
+            id = BenchFixture.SESSION_ID,
+            setup = "bench",
+            setupName = "bench",
+            provider = "bench",
+            title = "P0 benchmark",
+            model = null,
+            keepsOwnTranscript = false,
+            permissionMode = null,
+            imported = false,
+            notify = false,
+            cwd = null,
+            contextTokens = null,
+            maxImageEdge = null,
+            status = "idle",
+            lastActivity = 0.0,
+        )
+
     // launchMode="singleTop": an enrollment scan, or a notification tapped while the app is open,
     // lands here rather than in a second activity instance.
     override fun onNewIntent(intent: Intent) {