All tracked .sh files were stored as mode 100644 (non-executable), even
though the CI workflow and normal usage invoke several of them directly
(./scripts/build.sh) rather than through `bash`. On a fresh Linux
checkout this fails with a permission error.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Bash equivalent of the PowerShell installer change: delegates to
sync_managed_destination, adds --client/--platform for non-interactive
runs (falling back to the existing interactive prompts when omitted), and
requires --update-plugins to update already-installed plugins instead of
doing so by default.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>