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>

Cargo.toml

@@ -1,9 +1,9 @@
 [workspace]
 resolver = "2"
 members = [
-    "crates/lumen-core",
-    "crates/lumen-host",
-    "crates/lumen-client-rs",
+    "crates/punktfunk-core",
+    "crates/punktfunk-host",
+    "crates/punktfunk-client-rs",
     "tools/latency-probe",
     "tools/loss-harness",
 ]
@@ -14,15 +14,15 @@ edition = "2021"
 rust-version = "1.82"
 license = "MIT OR Apache-2.0"
 authors = ["unom"]
-repository = "https://git.unom.io/unom/lumen"
+repository = "https://git.unom.io/unom/punktfunk"
 
 [profile.release]
 opt-level = 3
 lto = "thin"
 codegen-units = 1
-# NOTE: deliberately NOT `panic = "abort"`. lumen-core ships as a cdylib/staticlib into
+# NOTE: deliberately NOT `panic = "abort"`. punktfunk-core ships as a cdylib/staticlib into
 # third-party apps (Swift/Kotlin/C) and its C ABI catches panics at the boundary
-# (`catch_unwind` → `LumenStatus::Panic`). `panic = "abort"` would make that guard a
+# (`catch_unwind` → `PunktfunkStatus::Panic`). `panic = "abort"` would make that guard a
 # no-op and let a stray panic abort the embedding application. Unwinding keeps the
 # documented isolation guarantee real.