Run the live CPUs at the performance governor during install

archiso boots on whatever governor the kernel defaults to, which on most
laptops ramps conservatively. Package extraction and the UKI build are both
CPU-bound, so pin performance for the whole install and put it back afterwards.

Reduced from #87 by @davydotcom, which also disabled every non-POLL cpuidle
state. That half is left out deliberately: C1 wake latency is 1us on current
hardware, and disabling it leaves POLL as the only idle state, so idle cores
busy-spin instead of halting. Package extraction is single-threaded, so on an
8-core laptop that is 7 cores burning power for no work — on a thermally
limited machine that costs the working core its turbo headroom, which is a
plausible way to make the install slower. #87 measured the two tweaks together
with a page-cache prefetch and an updatedb deferral, so the C-state
contribution was never isolated.

Scoped to the whole install rather than just the pacstrap window, which #87
used: finalize_limine_boot runs mkinitcpio and compresses a UKI, and is the
most purely CPU-bound phase there is.

Restoring only matters when an install fails and the user keeps using the live
environment; a successful one reboots out of it.

Co-Authored-By: David Estes <davydotcom@gmail.com>
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

configs/airootfs/usr/share/omarchy-iso/orchestrator/main.py

@@ -65,11 +65,15 @@ def main() -> int:
     info(f"Installing Omarchy for {ctx.username} → {ctx.target}")
 
     from .phases_impl import (
+        boost_cpu_governor,
         cleanup_bind_mounts,
         cleanup_protected_state,
         cleanup_target_hook_masks,
+        restore_cpu_governors,
     )
 
+    governors = boost_cpu_governor()
+
     success = False
     try:
         try:
@@ -85,6 +89,7 @@ def main() -> int:
         info("Installation complete.")
         return 0
     finally:
+        restore_cpu_governors(governors)
         cleanup_bind_mounts(ctx)
         cleanup_target_hook_masks(ctx)
         if not success:

configs/airootfs/usr/share/omarchy-iso/orchestrator/phases_impl.py

@@ -1396,6 +1396,40 @@ def _validate_pre_mounted_filesystems(ctx: InstallContext) -> None:
             raise RuntimeError(f"{crypttab} missing LUKS UUID {storage['luks_uuid']}")
 
 
+CPU_SYSFS = Path("/sys/devices/system/cpu")
+
+
+def boost_cpu_governor() -> dict[Path, str]:
+    """Run the live CPUs flat out for the install.
+
+    Package extraction and the UKI build are both CPU-bound, and archiso boots
+    on whatever governor the kernel defaults to. Writing an unsupported
+    governor just fails, so nothing needs probing first, and hosts without
+    cpufreq (most VMs) have no paths at all. Returns the prior governors.
+    """
+    saved: dict[Path, str] = {}
+    for path in sorted(CPU_SYSFS.glob("cpu*/cpufreq/scaling_governor")):
+        try:
+            saved[path] = path.read_text().strip()
+            path.write_text("performance\n")
+        except OSError:
+            saved.pop(path, None)
+
+    if saved:
+        info(f"› CPU governor set to performance ({len(saved)} CPUs)")
+    return saved
+
+
+def restore_cpu_governors(saved: dict[Path, str]) -> None:
+    """Only matters when an install fails and the user keeps using the live
+    environment — a successful one reboots out of it."""
+    for path, governor in saved.items():
+        try:
+            path.write_text(f"{governor}\n")
+        except OSError:
+            continue
+
+
 # ─────────────────────────────────────────────────────────────────────────────
 # cleanup_bind_mounts: invoked from main()'s finally so bind mounts get
 # unwound on success, failure, or interrupt. Idempotent.