Add scripts/macos-install-test.sh, a throwaway-user harness for exercising
install.sh the way a brand-new user would on macOS, plus the research note
that motivates the approach.
The harness has up/run/status/down/deep-reset subcommands. Because install.sh
writes only to the user home (pipx venv, ~/.bot-bottle, a PATH line) and never
installs the backend, deleting the account is a complete, deterministic reset
of the install surface. A disposable macOS VM can't stand in on M1/M2: the
Apple `container` backend needs Virtualization.framework, and running it inside
a guest VM requires nested virtualization (M3+ only), so a throwaway user is
the only way to reach the real host backend from a clean $HOME.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
