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/vendor/fec-rs/README.md

@@ -0,0 +1,73 @@
+# fec-rs
+
+[![CI](https://github.com/hgaiser/fec-rs/workflows/CI/badge.svg)](https://github.com/hgaiser/fec-rs/actions)
+[![Crates.io](https://img.shields.io/crates/v/fec-rs.svg)](https://crates.io/crates/fec-rs)
+[![Documentation](https://docs.rs/fec-rs/badge.svg)](https://docs.rs/fec-rs)
+
+A pure Rust Reed-Solomon erasure coding library with runtime SIMD acceleration.
+
+## Features
+
+- **Pure Rust** — No C/C++ dependencies or FFI. Everything is implemented in safe Rust
+  (with targeted `unsafe` for SIMD intrinsics).
+- **Runtime SIMD detection** — Automatically uses the fastest available instruction set
+  via `std::is_x86_feature_detected!`. A single binary works on all x86_64 systems.
+- **GF(2^8)** — Operates over the Galois field GF(2^8) with generating polynomial 29 (0x1D),
+  compatible with the Moonlight streaming protocol.
+- **Shard-by-shard encoding** — Incremental encoding via `ShardByShard` for streaming use cases.
+- **Reconstruction** — Reconstruct missing data and/or parity shards from any sufficient subset.
+
+## SIMD Acceleration
+
+On x86_64, the library automatically detects CPU features at runtime and uses
+the best available instruction set:
+
+- **GFNI + AVX2** — Single-instruction GF multiply on 32 bytes (Intel Alder Lake+, AMD Zen 4+)
+- **AVX2** — VPSHUFB split-table nibble lookup on 32 bytes
+- **GFNI + SSE** — Single-instruction GF multiply on 16 bytes
+- **SSSE3** — VPSHUFB split-table nibble lookup on 16 bytes
+- **Scalar** — Lookup table fallback
+
+## Parallel Encoding
+
+Enable the `parallel` feature for optional rayon-based parallel encoding:
+
+```toml
+fec-rs = { version = "0.1", features = ["parallel"] }
+```
+
+When enabled, large encode workloads automatically distribute parity shard
+computation across threads. Small workloads use the sequential path to avoid
+overhead.
+
+## Usage
+
+```rust
+use fec_rs::ReedSolomon;
+
+let rs = ReedSolomon::new(4, 2).unwrap();
+
+let mut shards: Vec<Vec<u8>> = vec![
+    vec![0, 1, 2, 3],
+    vec![4, 5, 6, 7],
+    vec![8, 9, 10, 11],
+    vec![12, 13, 14, 15],
+    vec![0, 0, 0, 0], // parity shard 1
+    vec![0, 0, 0, 0], // parity shard 2
+];
+
+// Encode parity
+rs.encode(&mut shards).unwrap();
+
+// Verify
+assert!(rs.verify(&shards).unwrap());
+
+// Simulate loss of shard 0
+let mut recovery: Vec<Option<Vec<u8>>> = shards.into_iter().map(Some).collect();
+recovery[0] = None;
+
+// Reconstruct
+rs.reconstruct(&mut recovery).unwrap();
+```
+
+License: BSD-2-Clause