renovate: Use weekly schedule instead of minimumReleaseAge (#106)

The minimumReleaseAge approach delays PRs but doesn't reduce their count -
if a package releases daily, we still get daily PRs, just 7 days late.

Switch to a schedule-based approach: all dependencies (except bcvk) are
updated only on Sundays (UTC). When Sunday arrives, Renovate proposes the
latest version available, skipping all intermediate releases from the week.

bcvk is excluded from the schedule and continues to update immediately.

Assisted-by: OpenCode (claude-opus-4-5@20251101)

Signed-off-by: John Eckersberg <jeckersb@redhat.com>

Author: jeckersb

renovate-shared-config.json

@@ -59,23 +59,18 @@
     }
   ],
   "packageRules": [
-    // Default: Wait 1 week before proposing updates to ensure stability
+    // Limit dependency updates to once per week to reduce PR churn
     //
-    // This prevents chasing every patch release and reduces PR noise from
-    // rapidly-updating dependencies (e.g., opencode-ai had 7 updates in 8 days).
-    {
-      "description": ["Wait 1 week before proposing updates to ensure stability"],
-      "matchPackageNames": ["/.*/"],
-      "minimumReleaseAge": "7 days"
-    },
-    // Exceptions: Pick up certain packages immediately
+    // Rapidly-updating dependencies (e.g., opencode-ai) can create excessive PRs.
+    // By scheduling updates to Sundays only, we get one PR per week with the
+    // latest version, skipping all intermediate releases.
     //
-    // Add rules here for packages that should bypass the default waiting period,
-    // such as our own projects or critical dependencies.
+    // Exception: bcvk updates immediately (excluded via negated regex).
     {
-      "description": ["Pick up bcvk packages immediately without waiting"],
-      "matchPackageNames": ["/^bcvk$/"],
-      "minimumReleaseAge": "0 days"
+      "description": ["Limit dependency updates to weekly (Sundays UTC) to reduce PR churn. bcvk is excluded and updates immediately."],
+      "matchPackageNames": ["!/^bcvk$/"],
+      "schedule": ["on sunday"],
+      "timezone": "UTC"
     },
     {
     // These files in these repos are synced from the bootc-dev/infra repository, which