The autonomous --open-pr run failed at `git commit` with
`sh: syntax error: unexpected "("`: R's system2() with captured output runs the
command through /bin/sh, and the commit message `feat(patches): ...` (and the
`^{commit}` / `ref:path` git refs in the trial-build gate) contain shell
metacharacters that were passed unquoted.
shQuote() every git argument in propose-patches.R's git() helper and in
trial-build-registry.R's base-ref reads. Reproduced the failure and verified the
fix against a real git repo (commit with "()" in the message now succeeds; a
`HEAD^{commit}` rev-parse resolves).