feat(native-usb): add 32-frame HD gameplay rumble and USB flight diagnostics

Preserve native frequency/amplitude timelines for DualSense PCM output,
remove the unsupported 64-frame path, and retain compatibility rumble for
other controllers. Use the validated 300 MHz sampling phase and restrict
non-bondable Classic discovery autoconnect to previously paired peers.

Buffer native-hub UART stdout and release USB IRQs around port-reset
callbacks. Add observer liveness and pre-SETUP root-response observations
without changing recovery behavior. Cover transport and haptics boundaries.

Record the user-accepted 0.108 trial: controls remained responsive and
rumble felt fine. Instrumentation changes timing; the disconnect root
cause and long-term reliability remain unqualified.

Validation: 624 tests, 11 affected firmware/probe builds, and on-device
concurrent USB and HD-auto-start checks. Private captures, generated
images, and unrelated working-tree files are intentionally excluded.

tests/test_bluepad32_classic_discovery_native.py

@@ -0,0 +1,73 @@
+from __future__ import annotations
+
+import os
+import shutil
+import subprocess
+from pathlib import Path
+
+import pytest
+
+
+def test_bluepad32_classic_discovery_native(tmp_path: Path) -> None:
+    root = Path(__file__).resolve().parents[1]
+    sdk = Path(
+        os.environ.get("PICO_SDK_PATH", root / "build" / "_deps" / "pico_sdk-src")
+    )
+    btstack = sdk / "lib" / "btstack"
+    bluepad = root / "external" / "bluepad32" / "src" / "components" / "bluepad32"
+    if (
+        not (btstack / "src" / "btstack.h").is_file()
+        or not (bluepad / "bt" / "uni_bt_bredr.c").is_file()
+    ):
+        pytest.skip("requires Pico SDK and Bluepad32 checkout")
+    compiler = shutil.which("cc") or shutil.which("gcc")
+    assert compiler is not None, "a host C compiler is required"
+    git = shutil.which("git")
+    assert git is not None, "Git is required to prepare the project patch"
+    relative = Path("src/components/bluepad32/bt/uni_bt_bredr.c")
+    patched = tmp_path / relative
+    patched.parent.mkdir(parents=True)
+    shutil.copyfile(bluepad / "bt" / "uni_bt_bredr.c", patched)
+    subprocess.run(
+        [
+            git,
+            "apply",
+            "--no-index",
+            f"--include={relative.as_posix()}",
+            str(root / "patches" / "bluepad32-sdl3-imu.patch"),
+        ],
+        cwd=tmp_path,
+        check=True,
+    )
+    executable = tmp_path / "classic_discovery_test"
+    subprocess.run(
+        [
+            compiler,
+            "-std=c11",
+            "-O2",
+            "-Wall",
+            "-Wextra",
+            "-Werror",
+            "-ffunction-sections",
+            "-fdata-sections",
+            f"-I{root / 'tests' / 'btstack_credit_batch_native_stubs'}",
+            f"-I{root / 'bluepad32_config'}",
+            f"-I{bluepad / 'include'}",
+            f"-I{btstack / 'src'}",
+            f"-I{btstack / 'platform' / 'embedded'}",
+            f"-I{btstack / '3rd-party' / 'bluedroid' / 'encoder' / 'include'}",
+            f"-I{btstack / '3rd-party' / 'bluedroid' / 'decoder' / 'include'}",
+            f"-I{btstack / '3rd-party' / 'yxml'}",
+            str(root / "tests" / "bluepad32_classic_discovery_test.c"),
+            str(patched),
+            str(bluepad / "bt" / "uni_bt_conn.c"),
+            str(btstack / "src" / "btstack_util.c"),
+            str(btstack / "src" / "btstack_run_loop.c"),
+            "-Wl,--gc-sections",
+            "-o",
+            str(executable),
+        ],
+        cwd=root,
+        check=True,
+    )
+    subprocess.run([str(executable)], cwd=root, check=True)