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/apple/Package.swift

@@ -1,21 +1,21 @@
 // swift-tools-version: 5.9
-// LumenKit — Swift wrapper around the lumen-core C ABI (lumen/1 client connector) plus the
-// SwiftUI/VideoToolbox presentation layer. Build LumenCore.xcframework first:
+// PunktfunkKit — Swift wrapper around the punktfunk-core C ABI (punktfunk/1 client connector) plus the
+// SwiftUI/VideoToolbox presentation layer. Build PunktfunkCore.xcframework first:
 //   bash ../../scripts/build-xcframework.sh   (on a Mac; see README.md)
 import PackageDescription
 
 let package = Package(
-    name: "LumenKit",
+    name: "PunktfunkKit",
     platforms: [.macOS(.v14), .iOS(.v17)],
     products: [
-        .library(name: "LumenKit", targets: ["LumenKit"]),
-        .executable(name: "LumenClient", targets: ["LumenClient"]),
+        .library(name: "PunktfunkKit", targets: ["PunktfunkKit"]),
+        .executable(name: "PunktfunkClient", targets: ["PunktfunkClient"]),
     ],
     targets: [
-        .binaryTarget(name: "LumenCore", path: "LumenCore.xcframework"),
+        .binaryTarget(name: "PunktfunkCore", path: "PunktfunkCore.xcframework"),
         .target(
-            name: "LumenKit",
-            dependencies: ["LumenCore"],
+            name: "PunktfunkKit",
+            dependencies: ["PunktfunkCore"],
             linkerSettings: [
                 // Rust staticlib system deps.
                 .linkedFramework("Security"),
@@ -23,8 +23,8 @@ let package = Package(
                 .linkedLibrary("resolv"),
             ]
         ),
-        // Development app shell (swift run LumenClient): connect form → stream + input.
-        .executableTarget(name: "LumenClient", dependencies: ["LumenKit"]),
-        .testTarget(name: "LumenKitTests", dependencies: ["LumenKit"]),
+        // Development app shell (swift run PunktfunkClient): connect form → stream + input.
+        .executableTarget(name: "PunktfunkClient", dependencies: ["PunktfunkKit"]),
+        .testTarget(name: "PunktfunkKitTests", dependencies: ["PunktfunkKit"]),
     ]
 )