Build zmx-backed persistent SSH terminals with CLI and TUI

[DeepakSilaych]

What changes

Replace the Bash/tmux implementation with a Go client and zmx-backed SSH sessions. A user can prepare a VM, select a default SSH host, create a named terminal, detach, and return to the same shell. Explicit detach and shell exit stop the connection; transient SSH failures reconnect to the original session identity.

• Implement init, set --host, new/n, attach/a, remove/rm, ls, detach, doctor, and completion. -h selects a host; --help shows help. Add new --detach, ls --json, and ls --quiet for scripts.
• Add an asynchronous Bubble Tea browser with filtering, host switching, create/attach/remove actions, terminal handoff, responsive layout, and persistent error messages.
• Install an embedded, platform-specific remote helper and SHA-256-verified zmx 0.8.1 without sudo. Use a private zmx namespace, validated arguments, a versioned SSH protocol, session IDs, and atomic local configuration.
• Replace obsolete npm packaging and wake-up hooks with cross-platform build/release scripts, generated completions, and updated user documentation.

Validation

• make test: race-enabled unit tests and go vet pass on macOS ARM64; the same Go checks also pass independently in Linux ARM64 Docker.
• Native macOS zmx tests: create, duplicate rejection, identity validation, remove, and empty list pass.
• Real OpenSSH + zmx in a disposable Debian Docker container: provisioning, aliases, host overrides, persistence across detach, forced SSH disconnect/reconnect, multiple clients, detach-all, shell exit, attach-only semantics, removal, TUI create/attach/return/remove, and isolation from ordinary zmx sessions pass.
• Built client and remote-helper targets for macOS/Linux on AMD64/ARM64. Inspected a rendered capture from the real TUI integration run.

Compatibility

This is the 0.6 development interface. Existing tmux sessions and ~/.sess data are left untouched; live tmux sessions cannot migrate to zmx. Session commands require key authentication available to OpenSSH batch mode. zmx is pinned to 0.8.1; unsupported managed versions are not silently replaced. Live sessions do not survive VM reboot/backend loss. Runtime integration was exercised with a macOS ARM64 client and Linux ARM64 VM; the other targets are cross-built.

Validation was run locally. No GitHub Actions workflows are included.