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>

clients/linux-session/Cargo.toml

@@ -0,0 +1,22 @@
+[package]
+name = "punktfunk-client-session"
+description = "punktfunk/1 Vulkan session binary — SDL3 window, ash presenter, terminal stats; the power-user / gamescope stream client"
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+authors.workspace = true
+repository.workspace = true
+
+[[bin]]
+name = "punktfunk-session"
+path = "src/main.rs"
+
+# Same Linux gating as the rest of the client stack; elsewhere this is a stub binary.
+[target.'cfg(target_os = "linux")'.dependencies]
+pf-presenter = { path = "../../crates/pf-presenter" }
+pf-client-core = { path = "../../crates/pf-client-core" }
+punktfunk-core = { path = "../../crates/punktfunk-core", features = ["quic"] }
+anyhow = "1"
+tracing = "0.1"
+tracing-subscriber = { version = "0.3", features = ["env-filter"] }