Master's windows-python-console-spawn-wait fix removed the plugin-add flake
this branch previously retried, so that retry is dropped entirely; the
branch keeps the changes that remain useful.
- Retry the immutable install step up to three attempts total with a
ten-second pause (bash on every platform): node-gyp's Node-header
download from nodejs.org intermittently times out, as observed on the
hosted node24-macos-x64 cell.
- Keep checkout credentials out of the build tree (persist-credentials:
false) so dependency-install scripts cannot read the embedded token.
- Failover runbook: drop the stray leading '#' before the Dependabot
paragraph on both sides.
- Hosted-runtime note: name the PR/commit ownership and UTC timestamps of
the cited runs and record the constraints a future self-hosted attempt
must satisfy; new note records the install retry decision.