selenium: right-size hub + chrome + edge memory limits (#28)

Edge node has been OOMKilled 51 times in 5 days (~1 every 2.4h) on a
1Gi memory limit. Chrome runs maxSessions=2 on the same 1Gi cap and
was idling at 684Mi — first concurrent session pushing the node to
~900Mi+ would be the next OOM. Hub was running at 766Mi against a 1Gi
limit (75%); no recent restarts but no headroom either.

Firefox node has been running at 2Gi memory limit for 9 days with
zero restarts — that is the right size for a Selenium 4.27 browser
node under our session profile (screen recording sidecar + 1080p
rendering + page captures). Match it.

Changes:
- Hub:    limit 1Gi -> 1.5Gi, request 512Mi -> 1Gi
- Chrome: limit 1Gi -> 2Gi,   request 512Mi -> 1Gi
- Edge:   limit 1Gi -> 2Gi,   request 512Mi -> 1Gi

CPU left alone on all three — observed utilization is well under the
existing limits (hub 54m / 500m, chrome 185m / 1, edge 11m / 1).

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

apps/selenium/selenium-grid.yaml

@@ -132,13 +132,18 @@ spec:
           initialDelaySeconds: 10
           periodSeconds: 5
           timeoutSeconds: 5
+        # Hub baseline working set ~766Mi on 2026-05-25 (75% of prior 1Gi
+        # limit). Bump to 1.5Gi / 1Gi to keep ~50% headroom; matches the
+        # stampede-buffer pattern documented for multus
+        # (feedback_k8s_cni_multus_sizing). CPU left alone — observed 54m
+        # against a 500m limit, no contention.
         resources:
           limits:
             cpu: 500m
-            memory: 1Gi
+            memory: 1536Mi
           requests:
             cpu: 250m
-            memory: 512Mi
+            memory: 1Gi
 ---
 apiVersion: apps/v1
 kind: Deployment
@@ -198,13 +203,18 @@ spec:
             port: 5555
           initialDelaySeconds: 15
           periodSeconds: 5
+        # Chromium-based browser node. Bumped from 1Gi -> 2Gi (req 512Mi
+        # -> 1Gi) on 2026-05-25 — Edge had 51 OOMKills in 5d on the
+        # original 1Gi cap (~1 OOM every 2.4h), and Chrome at maxSessions=2
+        # was running 684Mi idle on the same cap. Matches the Firefox node's
+        # tested-stable 2Gi limit. CPU unchanged.
         resources:
           limits:
             cpu: '1'
-            memory: 1Gi
+            memory: 2Gi
           requests:
             cpu: 500m
-            memory: 512Mi
+            memory: 1Gi
         volumeMounts:
         - mountPath: /dev/shm
           name: dshm
@@ -378,13 +388,18 @@ spec:
             port: 5555
           initialDelaySeconds: 15
           periodSeconds: 5
+        # Chromium-based browser node. Bumped from 1Gi -> 2Gi (req 512Mi
+        # -> 1Gi) on 2026-05-25 — Edge had 51 OOMKills in 5d on the
+        # original 1Gi cap (~1 OOM every 2.4h), and Chrome at maxSessions=2
+        # was running 684Mi idle on the same cap. Matches the Firefox node's
+        # tested-stable 2Gi limit. CPU unchanged.
         resources:
           limits:
             cpu: '1'
-            memory: 1Gi
+            memory: 2Gi
           requests:
             cpu: 500m
-            memory: 512Mi
+            memory: 1Gi
         volumeMounts:
         - mountPath: /dev/shm
           name: dshm