TECHO5 dev channel

Rolling test build for devices set to the dev update channel in Home Assistant. Not for everyday use: it is whatever is being worked on, and it is replaced in place.

Currently: v0.7.6-beta.2, the Echo Show 5 1st gen (checkers) work in progress. The 1st gen's microphones were silent because its converter comes up with both channel mutes set; they are now cleared with the input routing. The 2nd gen (cronos) is unaffected: it already had them off.

Devices on the stable channel never see this release. Built and attested by GitHub Actions from the checkers branch:
gh attestation verify echod-arm --repo HuskerMinion/techo5 --source-ref refs/tags/v0.7.6-beta.2