feat(client): Vulkan session binary — SDL3 + ash presenter MVP (phase 1)

punktfunk-session streams one --connect session in an SDL3 window: ash
swapchain with a transfer-only letterboxed blit of the software-decode
path (no graphics pipeline until the phase-2 dmabuf/CSC pass), the
ui_stream input-capture state machine on SDL events (scancode→VK table
cross-checked against the evdev one), gamepads via a new caller-pumped
GamepadService mode (SDL video owns the main thread here), and the
shell↔session stdout contract: {"ready":true}, per-window stats:
lines, JSON error + exit codes 0/2/3/4. Strict trust — no pin, no
connect. Design: punktfunk-planning linux-client-rearchitecture.md.

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

Cargo.toml

@@ -6,9 +6,11 @@ members = [
     "crates/punktfunk-host/vendor/usbip-sim",
     "crates/punktfunk-tray",
     "crates/pf-client-core",
+    "crates/pf-presenter",
     "crates/pf-driver-proto",
     "clients/probe",
     "clients/linux",
+    "clients/linux-session",
     "clients/windows",
     "clients/android/native",
     "tools/latency-probe",