TASK 48 slice 2: the app packs as a Microsoft Store MSIX

The manifest the Store route needs, and a real package built from it.

Packaging/Package.appxmanifest is a full-trust packagedClassicApp: EntryPoint
Windows.FullTrustApplication, uap10:TrustLevel=mediumIL,
uap10:RuntimeBehavior=packagedClassicApp, the rescap runFullTrust capability, and
webcam + microphone DeviceCapabilities. That combination is what lets the packaged
app launch the bundled ffmpeg as a child process and write to the user's profile;
an appContainer package would virtualise the recordings folder instead. x64 only,
en-US only (policy 10.7).

Packaging/Assets/ carries the four tiles the packer requires, generated from the
app's own Assets/llamacasty-logo.jpg by scripts/make-store-logos.py - listing art
and app art cannot drift.

scripts/package-msix.sh publishes Release win-x64 self-contained into
artifacts/msix-stage (a RID-less publish would copy every RID's ONNX native),
stages the manifest as AppxManifest.xml + Assets, and runs the Windows SDK's
makeappx. MSIX_PFX/MSIX_PFX_PASSWORD sign a package for a local test install; the
Store signs submissions. artifacts/ is gitignored.

First real package: artifacts/LlamaCasty.msix, 159 MB, 509 files, 'Package
creation succeeded'.

Schema traps found by packing (makeappx reports one error at a time):
Square310x310Logo and Wide310x150Logo are NOT uap:VisualElements attributes - they
live on uap:DefaultTile.

Guard: StorePackagingTests.The_package_manifest_declares_full_trust_camera_and_
microphone - identity/architecture, the full-trust application element, the three
capabilities, no appContainer VALUE (not the file text: the manifest's own comment
says the word), en-US only, and every referenced logo present.

Full suite 438/438, 0 warnings. Cold-start smoke test after the Velopack removal:
MainWindow loaded, no exceptions.

Packaging/Package.appxmanifest

@@ -0,0 +1,78 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  LlamaCasty — Microsoft Store MSIX manifest (TASK 48).
+
+  Full trust is the whole point of this file: the app records to the user's profile,
+  launches the bundled ffmpeg as a CHILD PROCESS, opens an ordinary Win32 folder picker,
+  and drives WebView2. None of that works in an AppContainer, so this is a
+  packagedClassicApp at mediumIL with the runFullTrust restricted capability.
+
+  ⛔ Do NOT change this to appContainer: recording silently starts writing to a
+  per-package virtualised folder and the output "vanishes" (TASK 48 item 6).
+
+  ⚠️ Before submission, replace Publisher with the exact Publisher value Partner Center
+  shows for the account, and PublisherDisplayName with its display name — a mismatch is
+  a certification rejection. The version is bumped per submission.
+-->
+<Package
+    xmlns="http://schemas.microsoft.com/appx/manifest/foundation/windows10"
+    xmlns:uap="http://schemas.microsoft.com/appx/manifest/uap/windows10"
+    xmlns:uap10="http://schemas.microsoft.com/appx/manifest/uap/windows10/10"
+    xmlns:rescap="http://schemas.microsoft.com/appx/manifest/foundation/windows10/restrictedcapabilities"
+    IgnorableNamespaces="uap uap10 rescap">
+
+  <Identity
+      Name="LlamaCasty"
+      Publisher="CN=LlamaCasty"
+      Version="1.0.0.0"
+      ProcessorArchitecture="x64" />
+
+  <Properties>
+    <DisplayName>LlamaCasty</DisplayName>
+    <PublisherDisplayName>LlamaCasty</PublisherDisplayName>
+    <Description>Live streaming to YouTube: scenes, sources, a webcam with background effects, alerts, chat and recording.</Description>
+    <Logo>Assets\StoreLogo.png</Logo>
+  </Properties>
+
+  <Dependencies>
+    <TargetDeviceFamily
+        Name="Windows.Desktop"
+        MinVersion="10.0.19041.0"
+        MaxVersionTested="10.0.26100.0" />
+  </Dependencies>
+
+  <!-- English only (Store policy 10.7): a second language here means the listing
+       description must be localised into it too. -->
+  <Resources>
+    <Resource Language="en-US" />
+  </Resources>
+
+  <Applications>
+    <Application
+        Id="LlamaCasty"
+        Executable="ytLive.exe"
+        EntryPoint="Windows.FullTrustApplication"
+        uap10:TrustLevel="mediumIL"
+        uap10:RuntimeBehavior="packagedClassicApp">
+      <uap:VisualElements
+          DisplayName="LlamaCasty"
+          Description="Live streaming to YouTube: scenes, sources, a webcam with background effects, alerts, chat and recording."
+          BackgroundColor="#171928"
+          Square150x150Logo="Assets\Square150x150Logo.png"
+          Square44x44Logo="Assets\Square44x44Logo.png">
+        <!-- The wide and 310 tiles live on DefaultTile, not on VisualElements — the
+             Windows 10 uap:VisualElements schema has no such attributes. -->
+        <uap:DefaultTile
+            Wide310x150Logo="Assets\Wide310x150Logo.png"
+            Square310x310Logo="Assets\Square310x310Logo.png" />
+      </uap:VisualElements>
+    </Application>
+  </Applications>
+
+  <Capabilities>
+    <rescap:Capability Name="runFullTrust" />
+    <DeviceCapability Name="webcam" />
+    <DeviceCapability Name="microphone" />
+  </Capabilities>
+
+</Package>