ci: post the daily Nanosoldier benchmark request from GitHub Actions (#63589)
The daily `runbenchmarks(isdaily = true)` request was a commit comment posted
on master by a cron job on the old PkgEval server. That server is dead, so no
daily benchmark has run since 2026-09-13.
Post the same comment from a scheduled workflow instead, at the same time of
day. Nanosoldier accepts the request from any author as long as it is on a
recent master commit, so the workflow's own token is enough. The daily
PkgEval request is left out: its runner was on the same dead server.
Assisted-by: Claude Code (Opus 5.5)