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/neovim/neovim.toml

@@ -0,0 +1,20 @@
+[package]
+name = "neovim"
+version = "0.11.1"
+description = "Hyperextensible Vim-based text editor"
+url = "https://neovim.io/"
+license = "Apache-2.0"
+
+[source]
+url = "https://github.com/neovim/neovim/archive/v${version}/neovim-${version}.tar.gz"
+sha256 = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+
+[dependencies]
+run = ["glibc", "lua", "libxml2", "unibilium", "libtermkey", "libvterm", "msgpack-c"]
+build = ["gcc", "cmake", "ninja", "pkg-config"]
+
+[build]
+system = "cmake"
+configure = """cmake -B build -G Ninja -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=Release"""
+make = """ninja -C build"""
+install = """DESTDIR=${PKG} ninja -C build install"""