merge(core): reconcile the W7/W8 client refactor with origin's shared-clipboard feature

origin/main landed the shared clipboard (design/clipboard-and-file-transfer.md) while
this branch split quic/msgs.rs -> quic/{caps,control,...} and client.rs ->
client/{mod,control,worker,pump,planes,...} (W7) and deleted the two monoliths. The
feature had modified both deleted files, so its delta is re-applied onto the split
instead of resurrecting the monoliths:

  - HOST_CAP_CLIPBOARD                         -> quic/caps.rs
  - MSG_CLIP_* / CLIP_* consts, the six Clip*
    structs, and their encode/decode impls     -> quic/control.rs (beside the clock codecs)
  - CtrlRequest::{ClipControl,ClipOffer} +
    Negotiated.host_caps                        -> client/control.rs
  - WorkerArgs.{clip_event_tx,clip_cmd_rx}      -> client/worker.rs
  - CLIP_EVENT_QUEUE                            -> client/planes.rs
  - NativeClient clip fields, the 7 clip_* /
    host_caps / next_clip methods, connect()
    channel wiring                              -> client/mod.rs
  - the control-task encode/decode arms and
    the clipboard-task spawn                     -> client/pump.rs

Cargo.lock reconciled (adds pf-clipboard), punktfunk-host/Cargo.toml unions the W6
pf-* subsystem deps with pf-clipboard, and include/punktfunk_core.h is the cbindgen
union (clipboard + rumble C-ABI). punktfunk-core builds --all-features and its 174
lib tests pass, including quic::tests::clip_loopback.

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

Cargo.lock

@@ -2798,6 +2798,23 @@ dependencies = [
  "windows 0.62.2 (git+https://github.com/microsoft/windows-rs?rev=a4f7b2cb7c63c6bb7fc77a2affe57145be1d8c4f)",
 ]
 
+[[package]]
+name = "pf-clipboard"
+version = "0.12.0"
+dependencies = [
+ "anyhow",
+ "ashpd",
+ "futures-util",
+ "libc",
+ "punktfunk-core",
+ "quinn",
+ "tokio",
+ "tracing",
+ "wayland-client",
+ "wayland-protocols",
+ "windows 0.62.2 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "pf-console-ui"
 version = "0.12.0"
@@ -3282,6 +3299,7 @@ dependencies = [
  "opus",
  "parking_lot",
  "pf-capture",
+ "pf-clipboard",
  "pf-driver-proto",
  "pf-encode",
  "pf-frame",