chore(tao): migrate decorated-window-tao to Compose 1.12.0-beta02

[kdroidFilter]

Why

Get ahead of the Compose 1.12 release: the no-AWT decorated-window-tao
backend drives Compose's internal androidx.compose.ui.scene.* APIs directly,
so it's the one module that breaks on a minor Compose bump. This PR does that
migration against 1.12.0-beta02 so we're ready to flip to 1.12.0 stable the
day it ships (just move the catalog line).

Rebased on main (was conflicting: the tao JetBrains-style refactor moved
every touched file into scene/ / popup/ / deco/ / ffi/, so the
migration was re-applied on the new layout rather than replayed textually).
1.12.0 stable is not out yet — latest published is 1.12.0-beta02.

What changed in the 1.12 ComposeScene API

• ComposeScene.render(canvas, nanoTime) removed → three steps:
  FrameRecomposer.performFrame(nanoTime) + ComposeScene.measureAndLayout() +
  ComposeScene.draw(canvas).
• Scene factories (Canvas/PlatformLayersComposeScene) drop coroutineContext
  • invalidate; now take a FrameRecomposer (which owns the frame clock) +
    invalidateLayout / invalidateDraw. The manual per-host BroadcastFrameClock
    and frameClock.sendFrame() calls are gone.
• ComposeSceneContext.createLayer: compositionContext → consumePointerInputOutside.
• ComposeSceneLayer.setContent(parentCompositionContext, content) + new abstract
  consumePointerInputOutside property.

Approach

Scene create/render/dispose plumbing is centralized in TaoSceneBundle
(scene/TaoSceneBundle.kt). Each host/popup/overlay stores a TaoSceneBundle?
and keeps val scene get() = sceneBundle?.scene, so the ~20 scene?.… call
sites per file are untouched — only create/render/close move. Future Compose
bumps touch one file for the shared logic.

Behaviour is kept at parity with the 1.11 path: the paced frameNs is still fed
to the frame clock for standalone popups, and every invalidation
(invalidateLayout/invalidateDraw + the recomposer's own) funnels into the
same coalescing frame scheduler that invalidate used before.

The offscreen scene test harness (TaoSceneTestHarness, added after the first
revision of this PR) moves onto the same bundle: its explicit
frameClock.sendFrame + second pumpUntilIdle is now performed inside
recordSceneToPicture → FrameRecomposer.performFrame, which flushes its own
dispatchers around the tick.

Note: SingleComposeSceneRenderingScope

Compose Desktop's AWT path wraps the three render calls in
SingleComposeSceneRenderingScope.render, but that method is Kotlin-internal
(JVM-public, module-private) and invisible to external backends. TaoSceneBundle
inlines performFrame → measureAndLayout → draw directly. The only thing
lost vs. upstream is its isRendering-guarded invalidation de-dup — which the
old Tao code didn't have either, and the FrameDispatcher coalescing covers it.

Fallout: AGP 9 / Java 17

Compose 1.12 also pulls AndroidX Compose 1.12 into examples:cmp-demo's Android
target, which requires AGP ≥ 9.1 and compileSdk 37. That cascades:

• agp 8.13.2 → 9.1.1 (9.2+ needs Gradle ≥ 9.4.1, we're on 9.4.0), cmp-demo
  compileSdk/targetSdk 35 → 37.
• android.builtInKotlin=false + android.newDsl=false: since AGP 9,
  com.android.application is rejected alongside the KMP plugin, which points at
  com.android.kotlin.multiplatform.library — a library plugin, unusable for
  cmp-demo (a KMP module that builds a real Android app) without splitting it into
  a separate :androidApp module. These are AGP's documented escape hatches.
• plugin-build/plugin jvmTarget 11 → 17 — AGP 9 artifacts are built for 17
  and can't be resolved by an 11-targeted consumer. User-visible: the Nucleus
  Gradle plugin now needs a Gradle daemon on JVM 17+ (mandatory since Gradle 9
  anyway; Gradle 8 + JVM 11 setups are no longer supported).
• Dropped a stray org.jetbrains.skia.Surface import from cmp-demo's
  commonMain — unused, and unresolvable on Android. That target had never
  compiled; it does now (verified assembleDebug).

Verification

JBR 21, BUILD SUCCESSFUL, ktlint + detekt + apiCheck clean:

• :decorated-window-tao:check — 78 tests pass, including the animation,
  pointer, popup, render and battery-drift suites that exercise the new frame
  path (--rerun-tasks).
• assemble across the whole project, incl. :examples:cmp-demo:assembleDebug
  (Android), the jni / jbr / jewel / material2 / material3 backends,
  graalvm-runtime, nucleus-application, and the tao examples.
• plugin-build: :plugin:check + :plugin:validatePlugins — 209/210 tests
  pass at jvmTarget 17.
• The preMerge check set for every module listed in the preMerge task.

Two pre-existing local failures, both reproduced on unmodified main and
unrelated to this PR (both are environment-specific, not Compose-related):
:fs-watcher:test hangs on the real-filesystem test, and LinuxSignerTest
fails at gpg --gen-key.

Not done: native runtime smoke tests on macOS / Windows / Linux (headful
window/popup behaviour).

Before merge

• Switch catalog compose line to 1.12.0 stable (not yet published)
• Run the native standalone-popup smoke tests on the three OSes
• Confirm the plugin's JVM 17 floor is acceptable as a released change