Voice mode broken in WSL2: /proc/asound/cards check fails with PulseAudio/RDP audio

Bug Description

Claude Code 2.1.83 introduced a /proc/asound/cards check for voice mode on Linux. This check breaks voice mode in WSL2, where audio is routed through WSLg's PulseAudio RDP pipe — there are no ALSA hardware sound cards, so /proc/asound/cards always returns --- no soundcards ---.

Voice mode works correctly on 2.1.81 (and 2.1.80). The regression was introduced in 2.1.83.

Environment

• Platform: WSL2 (Ubuntu 24.04) on Windows 11
• Audio path: WSLg → PulseAudio → RDP audio pipe (no ALSA hardware)
• Working version: 2.1.81
• Broken version: 2.1.83

Steps to Reproduce

1. Install Claude Code 2.1.83 on WSL2
2. Ensure sox and alsa-utils are installed
3. Create ~/.asoundrc to bridge ALSA → PulseAudio
4. Confirm PulseAudio is working: pactl info shows RDPSource/RDPSink
5. Attempt voice mode (push-to-talk) — fails silently

Root Cause

2.1.83 added a probe that reads /proc/asound/cards and checks for the string no soundcards. In WSL2, this file always contains --- no soundcards --- because audio is handled by PulseAudio over WSLg's RDP pipe, not by ALSA hardware drivers. The check should either:

1. Also check for PulseAudio sources (pactl list sources short) as a fallback
2. Skip the ALSA hardware check on WSL2 (detectable via /proc/sys/fs/binfmt_misc/WSLInterop or WSL_DISTRO_NAME env var)
3. Attempt audio capture regardless and fail gracefully rather than pre-checking hardware

Workaround

Downgrade to 2.1.81: ln -sf ~/.local/share/claude/versions/2.1.81 ~/.local/bin/claude

Impact

Users on WSL2 are stuck on 2.1.81 and missing important fixes in 2.1.83 (background agent visibility after compaction, large session resume improvements, tool result cleanup, startup latency fixes).