refactor(client): extract UI-agnostic plumbing into pf-client-core (phase 0)

Session pump, FFmpeg decode, PipeWire audio, SDL3 gamepads, keymap, trust
store, mDNS discovery, library client and Wake-on-LAN move verbatim from
clients/linux into crates/pf-client-core, shared with the upcoming Vulkan
session binary (punktfunk-planning: linux-client-rearchitecture.md).
The GTK client re-exports them at the crate root so every existing
crate::-path keeps resolving; its manifest drops the moved-only deps.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

clients/linux/src/main.rs

@@ -5,27 +5,19 @@
 //! mirrors the Apple client: persistent identity, TOFU prompt with the host fingerprint,
 //! SPAKE2 PIN pairing.
 
+// The UI-agnostic plumbing lives in `pf-client-core`, shared with the upcoming Vulkan
+// session binary (design: punktfunk-planning linux-client-rearchitecture.md, Phase 0).
+// Root re-exports keep every existing `crate::video`-style path resolving unchanged.
+#[cfg(target_os = "linux")]
+pub use pf_client_core::{audio, discovery, gamepad, keymap, library, session, trust, video, wol};
+
 #[cfg(target_os = "linux")]
 mod app;
 #[cfg(target_os = "linux")]
-mod audio;
-#[cfg(target_os = "linux")]
 mod cli;
 #[cfg(target_os = "linux")]
-mod discovery;
-#[cfg(target_os = "linux")]
-mod gamepad;
-#[cfg(target_os = "linux")]
-mod keymap;
-#[cfg(target_os = "linux")]
 mod launch;
 #[cfg(target_os = "linux")]
-mod library;
-#[cfg(target_os = "linux")]
-mod session;
-#[cfg(target_os = "linux")]
-mod trust;
-#[cfg(target_os = "linux")]
 mod ui_gamepad_library;
 #[cfg(target_os = "linux")]
 mod ui_hosts;
@@ -38,12 +30,8 @@ mod ui_stream;
 #[cfg(target_os = "linux")]
 mod ui_trust;
 #[cfg(target_os = "linux")]
-mod video;
-#[cfg(target_os = "linux")]
 mod video_gl;
 
-mod wol;
-
 #[cfg(target_os = "linux")]
 fn main() -> gtk::glib::ExitCode {
     app::run()