runners: drop CPU request 500m→100m on DM/AiStation.Linux/WorldBuilder

All 3 fleet nodes were at 99% CPU REQUEST allocation; the 6 new pods
from the previous commit (3 deployments × 2 replicas × 500m) couldn't
schedule. Idle runners actually use ~1m CPU per `kubectl top pods`;
the 500m request was significantly over-provisioned. Burst headroom
preserved by limits.cpu: 2000m unchanged.

Follow-up: similar request right-sizing pass across the rest of the
runner fleet is queued for a future morning-routine sweep — 25 cores
reserved for ~50m actual use is a large slack we can reclaim cluster-
wide.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/github-runner/github-runner.yaml

@@ -4273,8 +4273,11 @@ spec:
             - name: RUN_AS_ROOT
               value: "false"
           resources:
+            # Reduced from 500m → 100m 2026-05-26 because cluster CPU
+            # requests were at 99% across all 3 nodes; idle runners use ~1m.
+            # Burst headroom preserved by limits.cpu: 2000m.
             requests:
-              cpu: "500m"
+              cpu: "100m"
               memory: "1Gi"
             limits:
               cpu: "2000m"
@@ -4408,7 +4411,7 @@ spec:
               value: "false"
           resources:
             requests:
-              cpu: "500m"
+              cpu: "100m"
               memory: "1Gi"
             limits:
               cpu: "2000m"
@@ -4541,7 +4544,7 @@ spec:
               value: "false"
           resources:
             requests:
-              cpu: "500m"
+              cpu: "100m"
               memory: "1Gi"
             limits:
               cpu: "2000m"