Split the QEMU configs by host system and architecture

Replace qemu/<guest>-<arch>.ini with qemu/<guest>-<os>-<arch>.ini, where os is
linux or darwin, the name platform.system() reports. The accelerators move out
of the shared <guest>.ini into these files (KVM on Linux, HVF on macOS, TCG as
the fallback). The launchers pick the file from the host system and
architecture, and reject amd64 guests on macOS hosts, so no darwin-amd64 files
exist.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

qemu/fedora44.ini

@@ -1,6 +1,7 @@
 # QEMU configuration for the Fedora 44 virtual machine, shared by all
-# architectures. The machine type and architecture-specific devices are in
-# fedora44-<arch>.ini, which QEMU reads after this file.
+# architectures. The accelerators, machine type and
+# platform-specific devices are in fedora44-<os>-<arch>.ini (os is linux or darwin),
+# which QEMU reads after this file.
 #
 # run-fedora44.py fills in the file path placeholders below, writes the result
 # to <state dir>/qemu.ini and passes it to QEMU with -readconfig. Options that
@@ -10,16 +11,6 @@
 [name]
   guest = "fedora44"
 
-# Accelerators are tried in order: KVM on Linux, HVF on macOS, else emulation.
-[accel]
-  accel = "kvm"
-
-[accel]
-  accel = "hvf"
-
-[accel]
-  accel = "tcg"
-
 [memory]
   size = "8G"