perf(site-runtime): warm the next startup batch during the stagger delay and compile a batch's distinct units in parallel (review 2026-10-21 01/SR-P3)

DeployCompileValidator.WarmCompileCache dedupes script bodies/trigger
expressions across a batch and compiles them with Parallel.ForEach (half the
cores). CreateInstanceActorBatch starts the next batch's warm as it arms the
stagger timer; creation order and delay are unchanged. The warm's parsed
configs are reused at creation.

tests/ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests/Actors/DeploymentWarmThenGateTests.cs

@@ -292,8 +292,10 @@ public class DeploymentWarmThenGateTests : TestKit, IDisposable
 
         AwaitAssert(() =>
         {
-            // One compile, then repeated hits: the second pre-warm plus both PreStarts.
-            Assert.True(_compileCache.Hits >= 3,
+            // One compile, then repeated hits from both PreStarts. (The batch warm dedupes
+            // distinct bodies before compiling — review 2026-10-21 01/SR-P3 — so the second
+            // config no longer costs a warm-side lookup of its own.)
+            Assert.True(_compileCache.Hits >= 2,
                 $"expected the pre-warmed body to be served from cache, saw {_compileCache.Hits} hits");
         }, TimeSpan.FromSeconds(20));