errmsg_test.go now calls the function that emits each user-visible CLI
error message and asserts on the full text it returns, instead of
rendering format strings copied from production, so rewording any pinned
message fails the suite. The unknown-command message is driven through
the root command's action.
The signer-mismatch case signs a manifest with a throwaway gpg key and
is skipped where gpg is absent, like the repo's other signing tests.
The freshen mtime-presence test gives the scanned file an epoch mtime,
so it fails if recordEntry reads an absent manifest mtime as the epoch.
Model: opus-4-8 (first implementation); opus-5-5 (completion, this message)
clawbot