rename: lumen → punktfunk, everywhere

Full project rename, decided 2026-06-10:
- Crates/binaries: punktfunk-core / punktfunk-host / punktfunk-client-rs.
- C ABI: punktfunk_* symbols, Punktfunk* types, include/punktfunk_core.h,
  PUNKTFUNK_FEATURE_QUIC guard (header regenerated; cbindgen renames updated, incl.
  PUNKTFUNK_BTN_*/PUNKTFUNK_AXIS_* wire constants).
- Protocol: punktfunk/1 — control-plane magic LMN1 → PKF1, nonce salt lmn1 → pkf1.
  WIRE BREAK: clients must be rebuilt from this revision.
- Env knobs: PUNKTFUNK_VIDEO_SOURCE / PUNKTFUNK_COMPOSITOR / PUNKTFUNK_ZEROCOPY / ….
- Host config dir: ~/.config/punktfunk (the box's dir was migrated in place — the
  persistent identity is unchanged, pinned fingerprints stay valid).
- Swift package: PunktfunkKit + PunktfunkCore.xcframework + PunktfunkConnection
  (Sources/PunktfunkClient app + tests renamed with it); build-xcframework.sh updated.
- scripts/: 60-punktfunk.rules, punktfunk-host.service; OpenAPI doc regenerated.

Also: scripts/headless/run-headless-kde.sh — full headless Plasma bringup. Root cause of
"desktop but no apps/settings" over the stream: plasmashell launched without
XDG_MENU_PREFIX=plasma-, so the launcher resolved a nonexistent applications.menu and
rendered an empty menu. The script sets the complete KDE session env (menu prefix,
KDE_FULL_SESSION, session version) and rebuilds ksycoca before starting plasmashell.

Gate: 97/97 tests, clippy -D warnings (both feature sets), fmt, C-ABI harness PASS,
zero lumen references left outside .git.

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

crates/punktfunk-core/src/stats.rs

@@ -0,0 +1,55 @@
+//! Live counters for the frame-pacing / quality logic and the web UI.
+
+use std::sync::atomic::{AtomicU64, Ordering};
+
+/// Immutable snapshot, copied across the C ABI as `PunktfunkStats`.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub struct Stats {
+    pub frames_submitted: u64,
+    pub frames_completed: u64,
+    pub frames_dropped: u64,
+    pub packets_sent: u64,
+    pub packets_received: u64,
+    pub packets_dropped: u64,
+    pub fec_recovered_shards: u64,
+    pub bytes_sent: u64,
+    pub bytes_received: u64,
+}
+
+/// Atomic accumulators owned by a [`Session`](crate::session::Session). Snapshot to
+/// [`Stats`] for readers. `Relaxed` ordering is fine: these are monotonic counters
+/// read for display, never used to synchronize other memory.
+#[derive(Default)]
+pub struct StatsCounters {
+    pub frames_submitted: AtomicU64,
+    pub frames_completed: AtomicU64,
+    pub frames_dropped: AtomicU64,
+    pub packets_sent: AtomicU64,
+    pub packets_received: AtomicU64,
+    pub packets_dropped: AtomicU64,
+    pub fec_recovered_shards: AtomicU64,
+    pub bytes_sent: AtomicU64,
+    pub bytes_received: AtomicU64,
+}
+
+impl StatsCounters {
+    #[inline]
+    pub fn add(counter: &AtomicU64, n: u64) {
+        counter.fetch_add(n, Ordering::Relaxed);
+    }
+
+    pub fn snapshot(&self) -> Stats {
+        let l = Ordering::Relaxed;
+        Stats {
+            frames_submitted: self.frames_submitted.load(l),
+            frames_completed: self.frames_completed.load(l),
+            frames_dropped: self.frames_dropped.load(l),
+            packets_sent: self.packets_sent.load(l),
+            packets_received: self.packets_received.load(l),
+            packets_dropped: self.packets_dropped.load(l),
+            fec_recovered_shards: self.fec_recovered_shards.load(l),
+            bytes_sent: self.bytes_sent.load(l),
+            bytes_received: self.bytes_received.load(l),
+        }
+    }
+}