signal-sdk launches signal-cli without --config, so attachments land at
~/.local/share/signal-cli/attachments/ (XDG default) rather than
data/signal/. Document this in the Channel Info section and add a
troubleshooting entry explaining the symptom (voice messages silently
skipped, no transcript), how to confirm (ps aux | grep signal-cli), and
the automatic fallback the adapter uses.
Adds the /add-signal-v2 skill: a native Signal channel adapter wrapping
signal-sdk (signal-cli under the hood). No bot API — NanoClaw registers
as a full Signal account on a dedicated number or as a linked device.
Features: text, group & DM routing, voice transcription via whisper.cpp,
attachments, emoji reactions, @mention detection, quote-reply detection.
Troubleshooting note updated: GroupV2 group ID lives at
envelope.dataMessage.groupV2.id — not groupInfo.groupId (GroupV1/legacy).
