refactor(ci): use docker backend + agent placement for process-updates/weekly

Match the build-all cleanup: only the docker backend is used and arch placement
is via the agent label, so the kubernetes backend_options blocks (with arch
nodeSelector and tolerations) are dead. Convert them to docker resource blocks.
weekly-audit had no agent label (it relied on the nodeSelector), so add
agent: ${AGENT} with an AGENT column (artemis=amd64, gaia=arm64) per matrix row.

.crow/weekly-audit-missing.yaml

@@ -5,7 +5,7 @@
 #             its matching matrix row (via CI_PIPELINE_CRON).
 #   - manual: pick a target from the `weekly_audit_missing` dropdown
 #             ("all" = every os/arch).
-# Arch placement is via the arch nodeSelector (this family uses no agent label).
+# Arch placement is via the agent label (artemis=amd64, gaia=arm64).
 variables:
   weekly_audit_missing:
     description: "Manual run target: a specific <os>-<arch>, or 'all' for every os/arch."
@@ -37,70 +37,89 @@ when:
 
 skip_clone: true
 
+labels:
+  agent: ${AGENT}
+
 matrix:
   include:
     - OS: alpine-321
       ARCH: amd64
+      AGENT: artemis
       R_VERSION: 4.5.3
       IMG: alpine:3.24
     - OS: alpine-321
       ARCH: arm64
+      AGENT: gaia
       R_VERSION: 4.5.3
       IMG: alpine:3.24
     - OS: alpine-322
       ARCH: amd64
+      AGENT: artemis
       R_VERSION: 4.5.3
       IMG: alpine:3.24
     - OS: alpine-322
       ARCH: arm64
+      AGENT: gaia
       R_VERSION: 4.5.3
       IMG: alpine:3.24
     - OS: alpine-323
       ARCH: amd64
+      AGENT: artemis
       R_VERSION: 4.5.3
       IMG: alpine:3.24
     - OS: alpine-323
       ARCH: arm64
+      AGENT: gaia
       R_VERSION: 4.5.3
       IMG: alpine:3.24
     - OS: redhat-8
       ARCH: amd64
+      AGENT: artemis
       R_VERSION: 4.4.3
       IMG: redhat:8
     - OS: redhat-8
       ARCH: arm64
+      AGENT: gaia
       R_VERSION: 4.4.3
       IMG: redhat:8
     - OS: redhat-9
       ARCH: amd64
+      AGENT: artemis
       R_VERSION: 4.4.3
       IMG: redhat:9
     - OS: redhat-9
       ARCH: arm64
+      AGENT: gaia
       R_VERSION: 4.4.3
       IMG: redhat:9
     - OS: redhat-10
       ARCH: amd64
+      AGENT: artemis
       R_VERSION: 4.5.3
       IMG: redhat:10
     - OS: redhat-10
       ARCH: arm64
+      AGENT: gaia
       R_VERSION: 4.5.3
       IMG: redhat:10
     - OS: ubuntu-2204
       ARCH: amd64
+      AGENT: artemis
       R_VERSION: 4.4.3
       IMG: ubuntu:jammy
     - OS: ubuntu-2204
       ARCH: arm64
+      AGENT: gaia
       R_VERSION: 4.4.3
       IMG: ubuntu:jammy
     - OS: ubuntu-2404
       ARCH: amd64
+      AGENT: artemis
       R_VERSION: 4.4.3
       IMG: ubuntu:noble
     - OS: ubuntu-2404
       ARCH: arm64
+      AGENT: gaia
       R_VERSION: 4.4.3
       IMG: ubuntu:noble
 
@@ -132,7 +151,7 @@ steps:
       - /opt/R/$R_VERSION/bin/R -q -e 'pak::pak(c("git::https://codefloe.com/rpkgs/bincraft.git", "httr2", "jsonlite"))'
       - /opt/R/$R_VERSION/bin/R -q -e 'source("local/weekly-missing-binaries-audit.R")'
     backend_options:
-      kubernetes:
+      docker:
         resources:
           requests:
             memory: 2Gi
@@ -140,10 +159,3 @@ steps:
           limits:
             memory: 4Gi
             cpu: 2000m
-        nodeSelector:
-          kubernetes.io/arch: ${ARCH}
-        tolerations:
-          - key: 'CI'
-            operator: 'Equal'
-            value: 'true'
-            effect: 'NoSchedule'