build-arm64.yml: run natively on runner-arm64-linux, daily

The new arm64 runner (a Tart VM on the Mac mini) builds it at native
speed, so it runs daily like build.yml, an hour after it.

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

.forgejo/buildah-arm64

@@ -1,7 +1,8 @@
 #!/usr/bin/env bash
 # `buildah`, but `buildah build` builds for linux/arm64: build-arm64.yml runs
 # `just BUILDAH=.../buildah-arm64 build`, so the Justfile stays upstream's.
-# On runner-x86-linux the arm64 steps run under QEMU user emulation.
+# A no-op on an arm64 runner; on an x86_64 one (runner-x86-linux) the arm64
+# steps run under QEMU user emulation.
 if [[ ${1:-} == build ]]; then
   shift
   exec buildah build --platform linux/arm64 "$@"

.forgejo/workflows/build-arm64.yml

@@ -11,15 +11,16 @@ name: Build Aurora (arm64)
 # aarch64 kernel, the one Kinoite ships, from a stand-in akmods image
 # (.forgejo/akmods-arm64.sh), with no extra kmods.
 #
-# There's no arm64 runner: runner-x86-linux runs it under QEMU user
-# emulation (petersweb-infra, hosts/runner-x86-linux), many times slower
-# than native, hence weekly and a long timeout. It builds this repo's main
-# as build.yml last merged it, without merging upstream itself.
+# Runs natively on runner-arm64-linux (petersweb-infra, a Tart VM on the Mac
+# mini), daily, an hour after build.yml. It builds this repo's main as
+# build.yml last merged it, without merging upstream itself. (Until
+# 2026-11-04 it ran weekly under QEMU emulation on runner-x86-linux; it
+# still works there, slowly, through buildah-arm64.)
 #
 # Secret: REGISTRY_TOKEN, as build.yml. Variable (optional): REGISTRY_USER.
 on:
   schedule:
-    - cron: '0 8 * * 6'
+    - cron: '0 6 * * *'
   workflow_dispatch:
 
 concurrency:
@@ -34,8 +35,8 @@ env:
 
 jobs:
   build:
-    runs-on: runner-x86-linux
-    timeout-minutes: 1440
+    runs-on: runner-arm64-linux
+    timeout-minutes: 300
     steps:
       - uses: https://forge.quinefoundation.com/quine-global-labs/mirror-actions-checkout@v4
         with: