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>

tools/loss-harness/src/main.rs

@@ -2,20 +2,20 @@
 //!
 //! Drives access units through the in-process loopback at increasing loss rates, for
 //! both FEC schemes, and prints how many frames survive. A pure-software stand-in for
-//! `tc netem` that needs no network and runs anywhere `lumen_core` builds. The real M3
+//! `tc netem` that needs no network and runs anywhere `punktfunk_core` builds. The real M3
 //! harness adds `tc netem` jitter/reorder on the UDP path.
 
-use lumen_core::config::{Config, FecConfig, FecScheme, ProtocolPhase, Role};
-use lumen_core::error::LumenError;
-use lumen_core::session::Session;
-use lumen_core::transport::loopback_pair;
+use punktfunk_core::config::{Config, FecConfig, FecScheme, ProtocolPhase, Role};
+use punktfunk_core::error::PunktfunkError;
+use punktfunk_core::session::Session;
+use punktfunk_core::transport::loopback_pair;
 
 fn config(role: Role, scheme: FecScheme, drop_period: u32) -> Config {
     Config {
         role,
         phase: match scheme {
             FecScheme::Gf8 => ProtocolPhase::P1GameStream,
-            FecScheme::Gf16 => ProtocolPhase::P2Lumen,
+            FecScheme::Gf16 => ProtocolPhase::P2Punktfunk,
         },
         fec: FecConfig {
             scheme,
@@ -47,7 +47,7 @@ fn run(scheme: FecScheme, drop_period: u32, frames: usize, frame_len: usize) ->
                     completed += 1;
                 }
             }
-            Err(LumenError::NoFrame) => {} // unrecoverable at this loss rate
+            Err(PunktfunkError::NoFrame) => {} // unrecoverable at this loss rate
             Err(e) => panic!("unexpected error: {e}"),
         }
     }
@@ -59,7 +59,7 @@ fn main() {
     let frame_len = 100_000; // ~98 shards across 2 FEC blocks
     let periods = [0u32, 32, 16, 8, 6, 4, 3, 2];
 
-    println!("lumen loss-harness — 25% FEC, {frames} frames of {frame_len} bytes");
+    println!("punktfunk loss-harness — 25% FEC, {frames} frames of {frame_len} bytes");
     println!("(GF8 = P1/GameStream-compat, GF16 = P2/wall-breaker)\n");
     println!(
         "{:>10}  {:>9}  {:>14}  {:>14}",