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/hooks.rs

@@ -298,8 +298,8 @@ fn dispatch(
     // The two env-var mirrors (`PUNKTFUNK_ON_CONNECT_CMD` / `PUNKTFUNK_ON_DISCONNECT_CMD`) —
     // the zero-config siblings of `PUNKTFUNK_RECOVER_SESSION_CMD` for the simplest cases.
     let mirror = match kind {
-        "client.connected" => crate::config::config().on_connect_cmd.clone(),
-        "client.disconnected" => crate::config::config().on_disconnect_cmd.clone(),
+        "client.connected" => pf_host_config::config().on_connect_cmd.clone(),
+        "client.disconnected" => pf_host_config::config().on_disconnect_cmd.clone(),
         _ => None,
     };
     if let Some(cmd) = mirror {