feat(host/linux): amdgpu session clock pin — gpuclocks grows the AMD arm

nvclocks.rs -> gpuclocks.rs. PUNKTFUNK_PIN_CLOCKS=1 now also pins every
amdgpu card's power_dpm_force_performance_level to high for the host
lifetime (prior level restored on exit) — the measured AMD encode-
latency lever: VCN per-frame time doubles when a 60fps paced trickle
lets clocks sag (8 -> 4.4ms/frame at 1440p on the 780M with clocks
hot). Root-gated by sysfs ownership; non-root degrades to a logged
recipe (validated live on the AMD box). Opt-in stays deliberate:
box-wide power-management override, wrong on battery/Deck.

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

crates/punktfunk-host/src/main.rs

@@ -33,6 +33,9 @@ mod drm_sync;
 mod encode;
 mod gamestream;
 mod gpu;
+#[cfg(target_os = "linux")]
+#[path = "linux/gpuclocks.rs"]
+mod gpuclocks;
 mod hdr;
 mod inject;
 #[cfg(target_os = "windows")]
@@ -45,9 +48,6 @@ mod library;
 mod mgmt;
 mod mgmt_token;
 mod native_pairing;
-#[cfg(target_os = "linux")]
-#[path = "linux/nvclocks.rs"]
-mod nvclocks;
 mod pipeline;
 mod punktfunk1;
 mod pwinit;
@@ -135,7 +135,7 @@ fn real_main() -> Result<()> {
     // exit via the guard's Drop). No-op off NVIDIA / on the tool subcommands.
     #[cfg(target_os = "linux")]
     let _nv_clocks = match args.first().map(String::as_str) {
-        Some("serve") | Some("punktfunk1-host") => nvclocks::on_host_start(),
+        Some("serve") | Some("punktfunk1-host") => gpuclocks::on_host_start(),
         _ => None,
     };