Add dev/self-hosting packages: qemu, neovim, build tools

14 new packages in extra/:
- qemu-9.2.3, edk2-ovmf-202411 (QEMU + UEFI firmware for testing)
- squashfs-tools-4.6.1, xorriso-1.5.7, mtools-4.0.48 (ISO building)
- efibootmgr-18, efivar-39 (UEFI boot management)
- rsync-3.4.1, lz4-1.10.0, nasm-2.16.03 (build/transfer tools)
- neovim-0.11.1, htop-3.4.0, tmux-3.5a, libevent-2.1.12 (dev tools)

Total: 138 packages (67 core, 40 extra, 19 desktop, 12 gaming)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

extra/qemu/qemu.toml

@@ -0,0 +1,20 @@
+[package]
+name = "qemu"
+version = "9.2.3"
+description = "Machine emulator and virtualizer"
+url = "https://www.qemu.org/"
+license = "GPL-2.0"
+
+[source]
+url = "https://download.qemu.org/qemu-${version}.tar.xz"
+sha256 = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+
+[dependencies]
+run = ["glibc", "glib", "pixman", "zlib", "zstd", "libxml2", "curl", "sdl2"]
+build = ["gcc", "make", "meson", "ninja", "pkg-config", "python", "flex", "bison"]
+
+[build]
+system = "meson"
+configure = """meson setup build --prefix=/usr --buildtype=release -Dgtk=disabled -Dsdl=enabled -Dvnc=disabled -Ddocs=disabled -Dspice=disabled"""
+make = """ninja -C build"""
+install = """DESTDIR=${PKG} ninja -C build install"""