Add Finder mount and Homebrew cask install path

[totocaster]

Summary

• Add tp7 mount and tp7 unmount for mounting the TP-7 in Finder through macFUSE/FUSE.
• Make Finder mounting the default mode, read-write by default, with --read-only still available.
• Default mounts to a user-owned ~/TP-7 path, with numbered siblings when needed, so users do not need admin privileges for /Volumes.
• Keep tp7 unmount stateless: it discovers TP-7 mounts from the OS mount table and treats OS/Finder unmounts as normal.
• Add tp7 doctor runtime checks for macFUSE/Fuse and update docs/release packaging so Homebrew installs as a cask with macfuse as a dependency.

User impact

After installing the cask, users should be able to run:

brew install --cask totocaster/tap/tp7
tp7 mount

The Finder mount appears at ~/TP-7 by default. Users can unmount from Finder, Disk Utility, diskutil, or tp7 unmount without requiring CLI state files.

Notes

• macFUSE remains required for Finder integration on macOS; doctor now reports whether the runtime is installed.
• The mount implementation is read-write, but TP-7 firmware/protocol behavior can still reject unsupported operations. The first expected user-facing write paths are copying files, overwriting files, renaming files, deleting files, and editing metadata that maps cleanly to MTP operations.
• A previous direct hardware smoke reached the expected small-file upload/overwrite/stat path, then hit an MTP I/O error during recursive directory push. Generated smoke files were cleaned up from /memo.

Validation

• cargo fmt -- --check
• PKG_CONFIG_PATH="/usr/local/lib/pkgconfig:/opt/homebrew/lib/pkgconfig:${PKG_CONFIG_PATH:-}" cargo check
• PKG_CONFIG_PATH="/usr/local/lib/pkgconfig:/opt/homebrew/lib/pkgconfig:${PKG_CONFIG_PATH:-}" cargo clippy -- -D warnings
• PKG_CONFIG_PATH="/usr/local/lib/pkgconfig:/opt/homebrew/lib/pkgconfig:${PKG_CONFIG_PATH:-}" cargo test
• PKG_CONFIG_PATH="/usr/local/lib/pkgconfig:/opt/homebrew/lib/pkgconfig:${PKG_CONFIG_PATH:-}" cargo run -- doctor
• PKG_CONFIG_PATH="/usr/local/lib/pkgconfig:/opt/homebrew/lib/pkgconfig:${PKG_CONFIG_PATH:-}" cargo run -- mount --help
• PKG_CONFIG_PATH="/usr/local/lib/pkgconfig:/opt/homebrew/lib/pkgconfig:${PKG_CONFIG_PATH:-}" cargo run -- unmount
• scripts/update-homebrew-tap.sh against a temp tap repo, followed by ruby -c Casks/tp7.rb
• scripts/write-release-notes.sh generated cask-based install instructions