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>

clients/android/README.md

@@ -1,18 +1,18 @@
-# lumen Android client (later)
+# punktfunk Android client (later)
 
-Kotlin UI + MediaCodec (decode) + a thin JNI layer over the `lumen-core` C ABI.
+Kotlin UI + MediaCodec (decode) + a thin JNI layer over the `punktfunk-core` C ABI.
 
 ## Wiring
 
 1. Build the core as a shared library per Android ABI:
    ```sh
    rustup target add aarch64-linux-android armv7-linux-androideabi x86_64-linux-android
-   cargo build -p lumen-core --release --target aarch64-linux-android   # liblumen_core.so
+   cargo build -p punktfunk-core --release --target aarch64-linux-android   # libpunktfunk_core.so
    ```
    (Use `cargo-ndk` to handle the NDK toolchain/linker.)
-2. JNI shim: small C/Rust glue mapping `lumen_*` to Kotlin `external fun`s, bundling
-   `liblumen_core.so` into the APK's `jniLibs/`.
-3. Kotlin: client `LumenSession` → `lumen_client_poll_frame` on a decode thread → feed
+2. JNI shim: small C/Rust glue mapping `punktfunk_*` to Kotlin `external fun`s, bundling
+   `libpunktfunk_core.so` into the APK's `jniLibs/`.
+3. Kotlin: client `PunktfunkSession` → `punktfunk_client_poll_frame` on a decode thread → feed
    `MediaCodec` → render to a `SurfaceView` aligned to the display refresh.
 
 ## Status