Make workspace, agent, and schedule automation consistent (#2186)

* feat(workspaces): align agent and schedule automation

Make workspace identity the shared placement boundary for MCP and CLI, while caller identity determines parentage. Keep heartbeats minimal and cron-based without changing legacy rolling interval semantics.

* test(cli): expect canonical schedule cadence

* fix(automation): preserve workspace and schedule compatibility

* fix(automation): preserve compatibility edges

* fix(workspaces): align MCP lifecycle resolution

* fix(workspaces): preserve creation intent

* fix(workspaces): preserve branch and schedule identity

packages/protocol/src/schedule/cadence.ts

@@ -0,0 +1,27 @@
+/**
+ * Convert an exact rolling interval to an equivalent five-field cron cadence.
+ * Returns null when cron's calendar boundaries would change the interval.
+ */
+export function everyMsToFiveFieldCron(everyMs: number): string | null {
+  const minutes = everyMs / 60_000;
+  if (!Number.isInteger(minutes) || minutes <= 0) {
+    return null;
+  }
+  if (minutes < 60 && 60 % minutes === 0) {
+    return `*/${minutes} * * * *`;
+  }
+  if (minutes === 60) {
+    return "0 * * * *";
+  }
+  if (minutes % 60 !== 0) {
+    return null;
+  }
+  const hours = minutes / 60;
+  if (hours < 24 && 24 % hours === 0) {
+    return `0 */${hours} * * *`;
+  }
+  if (hours === 24) {
+    return "0 0 * * *";
+  }
+  return null;
+}