Pull the Linux-only single-instance D-Bus stack out of cli/mod.rs into
a new cli/linux_forward.rs:
- tauri_identifier (reads identifier from embedded tauri.conf.json)
- single_instance_bus_name + single_instance_object_path (D-Bus path
derivation matching tauri-plugin-single-instance)
- linux_bus_name_has_owner (zbus NameHasOwner wrapper)
- linux_is_primary_instance_running (pub)
- LinuxPlayerForwardResult enum (pub)
- linux_try_forward_player_cli_secondary (pub) — the heavy lifter:
forwards argv via D-Bus ExecuteCallback, then for list/search
commands reads the response file and prints to stdout
The whole submodule is `#[cfg(target_os = "linux")]` gated at the mod
declaration so non-Linux builds don't see it at all (cleaner than the
previous per-item gating).
Public surface preserved: lib.rs and main.rs keep importing
cli::linux_is_primary_instance_running and cli::LinuxPlayerForwardResult
unchanged via the linux-only pub use re-export.
cli/mod.rs: 696 → 550 LOC. Behaviour-preserving — same D-Bus protocol,
same response-file polling, same stdout output strings.
Psychotoxical