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.

Controls/TopBar.xaml

@@ -1,6 +1,7 @@
 <UserControl x:Class="ytLive.Controls.TopBar"
              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:helpers="clr-namespace:ytLive.Helpers"
              x:Name="TopBarRoot">
     <!-- LOGO / BRAND — clicking opens the in-app About overlay -->
     <Grid>
@@ -20,7 +21,10 @@
                 </ControlTemplate>
             </Button.Template>
             <TextBlock FontSize="22" FontWeight="Bold">
-                <Run Text="LlamaCas" Foreground="#e0e0e0"/><Run Text="ty" Foreground="#e94560"/>
+                <Run Text="LlamaCas" Foreground="#e0e0e0"/><Run Text="ty" Foreground="#e94560"/><Run
+                    x:Name="BuildIdStamp" Text="{x:Static helpers:BuildStamp.Id}" FontSize="9"
+                    BaselineAlignment="Superscript" Foreground="#8888aa"
+                    ToolTipService.ToolTip="{x:Static helpers:BuildStamp.Id}"/><Run Text=" " FontSize="4"/>
             </TextBlock>
         </Button>