feat(audio,windows): real Raw Input + low-level hook global PTT (SDD-083 / SDD-084)

The v1.0.0-rc.7 Windows backends were thread::sleep stubs that
reported optimistic L2GlobalHoldToTalk / L3GlobalWithMouseButtons
descriptors without actually registering for any global key events.
Surfaced on Windows verification as:
  * 'even press to talk key was set, still only the hold to talk
    button is work for talk'
  * 'and displayed as L2GlobalHoldToTalk(raw-input)'
  * 'cannot continuous transmission'

This commit implements the real backends:

  WindowsRawInputBackend (preferred Windows rung, SDD-083):
    * Hidden message-only window via
      CreateWindowExW(..., HWND_MESSAGE, ...).
    * RegisterRawInputDevices with RIDEV_INPUTSINK on
      Usage Page 0x01 / Usage 0x06 (keyboard) and 0x02 (mouse) so
      events fire globally — including when Chanora is unfocused.
    * WndProc handling WM_INPUT: GetRawInputData ->
      keyboard.VKey vs bound vk, or mouse.usButtonFlags vs bound
      side-button index. Down -> gate.set(true); up -> gate.set(false).
    * Dedicated chanora-rawinput thread runs GetMessageW /
      TranslateMessage / DispatchMessageW until stop() posts
      WM_QUIT via PostThreadMessageW.

  WindowsHookBackend (fallback rung, SDD-084):
    * SetWindowsHookExW(WH_KEYBOARD_LL) + WH_MOUSE_LL on a
      dedicated chanora-llhook thread.
    * Hook procs translate KBDLLHOOKSTRUCT.vkCode and
      MSLLHOOKSTRUCT.mouseData against the same shared
      AtomicBinding.
    * UnhookWindowsHookEx on teardown.

  Both backends:
    * Honest descriptor() reporting: backends start reporting
      L0Focused; level upgrades to L2 / L3 only after a real
      arming success (RegisterRawInputDevices or SetWindowsHookEx
      returning Ok). This fixes the 'L2 reported but doesn't fire'
      complaint by making the badge tell the truth — if Raw Input
      registration fails at runtime the user sees the L0Focused
      info-icon explanation sheet instead of being told L2 works.
    * AtomicBinding (class / vk / mouse_btn) for lock-free hot
      path. Translation lives in
      crates/chanora_audio/src/ptt_backends/windows_keymap.rs
      which maps Flutter LogicalKeyboardKey.keyLabel strings
      (e.g. 'Space', 'F10', 'A') to Win32 VK_* codes; mouse
      side-button bitmask strings ('mouse-side-button:8' /
      ':16') to RawInput button indices (4 / 5).
    * Per-thread context (thread_local RefCell) carries the
      gate + binding to the WndProc / hook proc without needing
      raw-pointer user-data plumbing.

  Diagnostic logging:
    * AudioEngine::start now logs default_input_config and
      default_output_config explicitly with the channels /
      sample_rate / sample_format that cpal reports, so a
      build_*_stream failure on locale-specific Windows hosts
      (reported on ko-KR Windows 11 as 'Start Audio Button not
      work') becomes diagnosable from the stderr log alone.
    * build_output_stream surfaces the requested config in the
      tracing::error! record on failure.

  Privacy (DEC-027 / SDD-090): the windows.rs and
  windows_keymap.rs hot paths NEVER log raw VKs, scan codes,
  keysyms, key labels, or button identifiers. Only the
  platform-neutral input class ('keyboard' /
  'mouse-side-button') and the backend id appear in the tracing
  stream. The SDD-090 PttSanitizer Layer is the defence-in-depth
  net but this code does not rely on it.

  Tests: 4 new windows-only unit tests in windows_keymap (ASCII
  letters / digits / Space + Fn / unknown / mouse button index).
  They compile only under cfg(target_os = "windows") so the
  Linux workspace test count is unchanged at 59/0/3.

  Cargo deps: adds windows = '0.54' (target_os = windows) with
  the feature set needed for RawInput + hooks. 0.54 matches
  the version already transitive through the workspace.

Verified on Linux: cargo check --workspace clean, cargo test
--workspace 59/0/3 (windows-gated tests skip on Linux). The
real exercise of this commit will happen on the Korean Windows
11 host (100.84.219.45) at the next build.

Cargo.lock

@@ -388,6 +388,7 @@ dependencies = [
  "tokio",
  "tracing",
  "tsclientlib",
+ "windows",
  "zbus",
 ]