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.

ytLive.csproj

@@ -19,6 +19,30 @@
     <Page Remove="ytLive.Tests\**" />
   </ItemGroup>
 
+  <!-- Per-build identity stamp (2026-09-04): takes 1–6 could not be attributed to an
+       exact binary — render perf "fixes" were being judged against builds we could not
+       prove were running. A fresh GUID per build makes an incremental compile impossible
+       (that is the point: every exe you launch was compiled NOW), the wordmark shows the
+       id, and startup.log records id + build time. -->
+  <Target Name="GenerateBuildStamp" BeforeTargets="CoreCompile">
+    <PropertyGroup>
+      <BuildStampFile>$(IntermediateOutputPath)BuildStamp.g.cs</BuildStampFile>
+      <BuildStampId>$([System.Guid]::NewGuid().ToString('N').Substring(0,8))</BuildStampId>
+      <BuildStampTime>$([System.DateTime]::Now.ToString('yyyy-MM-dd HH:mm:ss'))</BuildStampTime>
+    </PropertyGroup>
+    <ItemGroup>
+      <BuildStampLines Include="// &lt;auto-generated&gt; Per-build identity (ytLive.csproj GenerateBuildStamp)."/>
+      <BuildStampLines Include="// Shown as the wordmark superscript and logged at startup: proof of which"/>
+      <BuildStampLines Include="// binary produced a test recording (2026-09-04). Never edit by hand."/>
+      <BuildStampLines Include="namespace ytLive.Helpers%3B"/>
+      <BuildStampLines Include="public static class BuildStamp { public const string Id = &quot;$(BuildStampId)&quot;%3B public const string BuiltLocal = &quot;$(BuildStampTime)&quot;%3B }"/>
+    </ItemGroup>
+    <WriteLinesToFile File="$(BuildStampFile)" Lines="@(BuildStampLines)" Overwrite="true" WriteOnlyWhenDifferent="false" />
+    <ItemGroup>
+      <Compile Include="$(BuildStampFile)" />
+    </ItemGroup>
+  </Target>
+
   <ItemGroup>
     <Resource Include="Assets\llamacasty-icon.png" />
     <Resource Include="Assets\llamacasty-logo.jpg" />