Hermes Agent STT fixture provenance

This minimal module contains the exact _prepare_local_audio patch context extracted from the agent image inherited by Dockerfile.hermes-webui:

Image: registry.bstein.dev/bstein/hermes-agent@sha256:81970563e542f0720773e72297810b3a844b83e381e278f25c0916c78d930107
OCI platform manifest: sha256:9b4c00a25fd08f0df3bcb800d755bd48576fb65af5ab0df40058fbb78a147e43
Upstream Hermes revision: 9de9c25f620ff7f1ce0fd5457d596052d5159596
Full upstream tools/transcription_tools.py SHA-256: d7d7df56b98dfadc0a7c08d5addd02db4e3106e6fd3b753e9241c23145eb2951

Tests execute the production patcher against this source fragment and then run its real ffmpeg conversion boundary with browser-produced bytes.