diag(build): per-build GUID stamp + resolve/blit timing split (take-6 attribution failure)

Take 6 measured render 35-41ms — WORSE than take 5's 25.5 — and the run could
not be attributed to a binary: exe mtime != build contents (incremental builds
serve stale exes; a source edit without rebuild is a silent old binary). Three
takes of a perf saga had been judged against builds nobody could prove.

- ytLive.csproj GenerateBuildStamp target: fresh GUID per compile (writes
  obj/BuildStamp.g.cs -> Helpers/BuildStamp.Id/BuiltLocal). Deliberately defeats
  incremental lies: every 'dotnet build' recompiles the app project.
- Wordmark shows the id as a superscript (TopBar.xaml, x:Static, 9px grey
  BaselineAlignment=Superscript); startup.log records 'Build <id> (compiled
  <time>)' so every take is cross-readable with the visible UI.
- FramePump stats split the tick: 'avg render Xms (resolve Y), avg submit Z' —
  the resolver is timed separately (wrapper resolver on per-tick paths; bake
  keeps the raw one) so take 7 names the hot half of 'render' with data.
- Fixed a latent transition-clock bug found on the way: lastTick now restarts
  every frame (the branch rework had restarted it only during transitions,
  letting a transition begun after idle complete instantly on its first Tick).

ONE integration test family: BuildStampTests (unit: shape) +
BuildStampDisplayTests (RealApp, namescoped FindName on TopBar proves the
wordmark SHOWS the id). 47/47 per-class green, clean build 0 warnings. Docs
same commit. User's top-bar/session spec (re-sent twice) + settled Q&A
decisions folded into HANDOFF Unit B — next work unit after take 7 verdict.

App.xaml.cs

@@ -26,6 +26,9 @@ public partial class App : Application
             AppLog.Write(args.Exception, "Dispatcher unhandled exception");
 
         AppLog.Write("App OnStartup begin");
+        // Attribution (2026-09-04): every take must be traceable to the exact binary
+        // that produced it — the wordmark superscript shows this same id.
+        AppLog.Write($"Build {ytLive.Helpers.BuildStamp.Id} (compiled {ytLive.Helpers.BuildStamp.BuiltLocal})");
 
         // Velopack auto-update bootstrap — checks for updates on startup and
         // applies them (the app restarts automatically if an update is found).