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>

crates/pf-presenter/Cargo.toml

@@ -0,0 +1,24 @@
+[package]
+name = "pf-presenter"
+description = "The Vulkan session presenter — SDL3 window, ash swapchain, frame present, input capture; the stage-2 presenter of punktfunk-planning linux-client-rearchitecture.md"
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+authors.workspace = true
+repository.workspace = true
+
+# Same Linux gating as the rest of the client stack.
+[target.'cfg(target_os = "linux")'.dependencies]
+pf-client-core = { path = "../pf-client-core" }
+punktfunk-core = { path = "../punktfunk-core", features = ["quic"] }
+
+# `loaded` dlopens libvulkan at runtime (no link-time dependency — GPU-less boxes still
+# start and fail into a clean error). `ash` on sdl3 types SDL_Vulkan_CreateSurface with
+# ash 0.38 handles so the surface hands over without transmutes.
+ash = { version = "0.38", features = ["loaded"] }
+sdl3 = { version = "0.18", features = ["hidapi", "ash"] }
+
+async-channel = "2"
+anyhow = "1"
+tracing = "0.1"