ci(release): include manifest path in the ReleaseNotes-write failure warning

Addresses the #32 review nit: the catch warning now names the built manifest (like
the missing-path warning) so logs identify which file failed to update.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: tablackburn

build.psake.ps1

@@ -93,7 +93,7 @@ Task -Name 'UpdateReleaseNotes' -Depends 'Build' -Description 'Set built manifes
     catch {
         # Keep publishing unblocked: a failure here just leaves the manifest's existing
         # ReleaseNotes in place rather than aborting the release.
-        Write-Warning "Failed to set ReleaseNotes on the built manifest ($($_.Exception.Message)); leaving it unchanged."
+        Write-Warning "Failed to set ReleaseNotes on the built manifest '$builtManifest' ($($_.Exception.Message)); leaving it unchanged."
     }
 }