boost v1.2.91

What's changed

Other changes

• cli: log the real exit code for --help and usage errors (#723)
• fix: five exit-70 crashes on bad paths/data become framed errors (#721)
• docs(demo): re-record demo.gif against the current CLI (#724)
• drift: hint boost tap <tap> when source-missing means untapped (#719)
• batch: train-11 — four PRs in one release (#719 #721 #723 #724) (#726)