Sort postFlushCbs to ensure refs are set before lifecycle hooks

Editor assessment

The header `fix(runtime-core/scheduler): sort postFlushCbs to ensure refs are set before lifecycle hooks (#1854)` states the changed behavior directly, so a reader grasps what was fixed and where without consulting the diff. The `fix` type is accurate and the compound scope `runtime-core/scheduler` pinpoints the affected sub-area. The trailing reference (`#1852`) is a well-formed, meaningful footer tying the change to its tracked issue. Style is clean — imperative mood, no trailing period, reasonable length. The message remains a one-liner with no account of the underlying cause, which only a body could supply; that keeps it a strong, publishable example rather than a teaching one.