refactor(host/W6.1): extract the config() global into the pf-host-config leaf crate

Third de-coupling for the host crate carve (plan §W6.1 leaf). HostConfig + the config()
OnceLock (config.rs, pure std, zero deps) move to a new pf-host-config leaf so every
subsystem crate (pf-encode/pf-capture/pf-vdisplay/pf-gpu) can read process config WITHOUT
depending on the orchestrator. 34 crate::config::config() call sites across 19 files
repoint to pf_host_config::config(). thread_qos stays in the host for now (it calls
session_tuning::on_hot_thread — its own leaf-ification rides the encode carve).

Granular-crate decision (supersedes the plan's single pf-media): split capture/encode/
vdisplay into separate crates rather than one broad crate — the capture↔encode cycle is
broken by a shared frame-types leaf, and vdisplay→encode (can_open_another_session) is a
legal one-way edge since encode never references vdisplay.

Verified: Linux (home-worker-5) clippy -p pf-host-config -p punktfunk-host --all-targets
-D warnings; Windows (192.168.1.158) clippy --features nvenc,amf-qsv --all-targets green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/punktfunk-host/src/gamestream/mod.rs

@@ -64,7 +64,7 @@ pub const SERVER_CODEC_MODE_SUPPORT: u32 = SCM_H264 | SCM_HEVC | SCM_AV1_MAIN8;
 /// whenever the desktop is HDR, and a client HDR request makes the GameStream video path proactively
 /// enable advanced color on the per-session virtual display so PQ flows even from an SDR desktop.
 pub fn host_hdr_capable() -> bool {
-    cfg!(target_os = "windows") && crate::config::config().ten_bit
+    cfg!(target_os = "windows") && pf_host_config::config().ten_bit
 }
 
 /// Stable host identity + advertised capabilities, shared across control-plane handlers.