A head no check runs on, such as a docs-only push that path filters keep
every workflow off, never woke the watch: an empty check list was treated
only as a failed host read. The watch now records when the head was first
read without any check. If none shows up within 15 minutes, it wakes the
thread once saying no checks reported, as an update rather than a pass.
A check seen on the head clears it, so later empty reads are still treated
as failed reads, and a new head starts it again.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>