Patch BasiliskII to allow custom extfs volume name (default Unix → Outside World)

[bryanwintermute]

Background

BasiliskII's extfs implementation hardcodes the volume name "Unix" in extfs_unix.cpp. Mac OS Finder rename attempts are silently ignored — the kid (or operator) cannot rename the volume from inside Mac OS.

For a kid-handoff chimebox, "Unix" is meaningless and feels technical. Infinite Mac uses "The Outside World" for the equivalent concept in their browser-based emulator. We should adopt the same name.

Scope

• Patch BasiliskII source to make the extfs volume name configurable via a new prefs entry (e.g. extfsname Outside World) with sensible default
• Build BasiliskII from source with our patch (current basiliskii role apt-installs the Debian build)
• Add a "build from source" path to pi/ansible/roles/basiliskii/tasks/main.yml
• Update group_vars/all.yml + basiliskii-prefs.j2 to set extfsname appropriately
• Consider upstreaming the patch

Pairs with

• Custom Outside World icon for extfs volume #5 (custom volume icon) — same source-level work, do together
• Research spike: port Infinite Mac's runtime disk add/remove patch to native BasiliskII #8 (their fork has BasiliskII patches; investigate whether they've already solved this)