C2 Task B process trace and extra format check, 2026-10-20 14:14 UTC+8 (sox 14.4.2 installed from Debian at 14:13 because the registry says 'requires: sox')

Programs executed during the whole Task B script (strace -f -e execve):
     12 execve("/workspace/triedagents-tools/runs/2026-10-20/tools/cli-anything/hubvenv/bin/cli-anything-audacity"
      1 execve("/workspace/triedagents-tools/runs/2026-10-20/tools/cli-anything/hubvenv/bin/python3"
=> sox was never run; no Audacity on the box or in the trace.

utils/sox_backend.py is imported only by tests/test_full_e2e.py:
hubvenv/lib/python3.13/site-packages/cli_anything/audacity/tests/test_full_e2e.py

core/export.py header: Uses ONLY Python stdlib (wave, struct, math) for WAV rendering.
core/export.py lines 204-209:
    if fmt == "WAV":
        write_wav(output_path, mixed, sample_rate, out_channels, bit_depth)
    else:
        # For non-WAV formats, write a WAV first and note that conversion
        # requires external tools
        write_wav(output_path, mixed, sample_rate, out_channels, bit_depth)

Extra (not in the plan): export render with presets flac, mp3, ogg:
  flac: sox execs 0
  mp3: sox execs 0
  ogg: sox execs 0
1c4267428d15ab5c360855ffa0e35495  out.flac
1c4267428d15ab5c360855ffa0e35495  out.mp3
1c4267428d15ab5c360855ffa0e35495  out.ogg
1c4267428d15ab5c360855ffa0e35495  out.wav
out.mp3 first bytes:  R I F F 274 \t 004 \0 W A V E  ffprobe: wav
out.flac first bytes:  R I F F 274 \t 004 \0 W A V E  ffprobe: wav
out.ogg first bytes:  R I F F 274 \t 004 \0 W A V E  ffprobe: wav
The CLI's JSON for an mp3 export said: {"format": "MP3", "file_size": 264644, "duration": 3.0}