chore(profiling): instrument plugin-load hot paths (v1.4.9 R3)

Bump AutoTranslate-warmup and FilterAllTabs log-level from Debug to
Information so the xllog tail surfaces them without a Debug filter.
Wrap MessageStore.Connect and MessageStore.Migrate in Stopwatches so
the SQLite open and migration-chain costs are visible too.

Sub-Task 3.4 Befund on v1.4.8-baseline (4 reloads, medians):
- MessageStore.Connect: 50.5 ms
- MessageStore.Migrate:    2 ms
- MessageManager.FilterAllTabs: 68.5 ms
- AutoTranslate warmup:  108 ms
- UiBuilder HITCH:       108.9 ms

Outcome D — none of the three dominates the 200 ms threshold. The
ChatTwo "300 ms" comment for AutoTranslate is falsified at ~108 ms;
SQLite is not the bottleneck (52.5 ms total); FilterAllTabs runs on
the worker thread and only competes for CPU slots. The HITCH is left
unexplained by these probes, which keeps Hypothesis c (multi-window
WindowSystem.Draw initial pass) as the main R2 suspect to be
validated by the R1 lazy-window refactor.

Logs stay in as belt-and-suspenders for future plugin-load
regressions.

HellionChat/MessageManager.cs

@@ -206,7 +206,10 @@ internal class MessageManager : IAsyncDisposable
                 Plugin.LogProxy.Error(ex, "Error in FilterAllTabs");
             }
 
-            Plugin.LogProxy.Debug($"FilterAllTabs took {stopwatch.ElapsedMilliseconds}ms");
+            // v1.4.9 R3 profiling: Information so the xllog tail surfaces this
+            // without a Debug filter. Belt-and-suspenders for future plugin-load
+            // regressions; remains in place after Sub-Task 3.4 Befund.
+            Plugin.LogProxy.Information($"FilterAllTabs took {stopwatch.ElapsedMilliseconds}ms");
         });
     }