Remove legacy WPF app, flatten WinUI project to repo root, rename namespace

The repo carried two parallel UIs (WPF + WinUI) sharing Models/Services via
cross-directory Link includes. Now that WinUI is the only frontend, collapse
the structure so the WinUI project IS the repo root instead of a nested
sibling folder:

- Delete the WPF project entirely (App.xaml, MainWindow.xaml, csproj) and its
  bin/obj output
- Move AmiReel.WinUI/* up to the repo root (App, MainWindow, MainPage,
  DialogHelper, Assets, Package.appxmanifest, app.manifest, Properties,
  .github/instructions, AGENTS.md) via git mv, preserving history
- Rename AmiReel.WinUI.csproj -> AmiReel.csproj; regenerate the solution as
  AmiReel.slnx (the newer XML solution format) with a single project
- Rename namespace AmigaDB.VideoRenderer.{Models,Services} -> AmiReel.{...}
  and AmiReel_WinUI -> AmiReel across all files, including the embedded
  ffmpeg/ffprobe resource logical names in the csproj and ToolExtractor
- Models/ and Services/ no longer need the Link-based cross-directory
  <Compile Include>; they're picked up by the SDK's default globbing now
  that they live under the project directory
- Rename assets/ -> branding/ (source icon art) to avoid a case-insensitive
  collision with Assets/ (packaged tile art) once both sit at repo root
- Merge the two .gitignore files into one; track the PublishProfiles pubxml
  files instead of ignoring them (no secrets, and they keep publish
  reproducible across machines) as branding, gitignore, etc.
- Simplify publish-win-x64.ps1 (drop the -Target Wpf/WinUI switch, there's
  only one target now) and rewrite README.md to describe the single-project
  layout, build/run/publish commands, and file structure

Verified: dotnet build succeeds for both AmiReel.csproj and AmiReel.slnx, and
the built exe launches and renders identically to before the move.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

publish-win-x64.ps1

@@ -1,8 +1,5 @@
 [CmdletBinding()]
-param(
-    [ValidateSet('WinUI', 'Wpf')]
-    [string]$Target = 'WinUI'
-)
+param()
 
 $ErrorActionPreference = 'Stop'
 
@@ -14,41 +11,21 @@ if (-not (Test-Path $ffmpeg) -or -not (Test-Path $ffprobe)) {
     throw 'Add ffmpeg.exe and ffprobe.exe to ThirdParty before publishing.'
 }
 
-switch ($Target) {
-    'WinUI' {
-        $projectPath = Join-Path $projectDir 'AmiReel.WinUI\AmiReel.WinUI.csproj'
-        $releaseDir = Join-Path $projectDir 'AmiReel.WinUI\bin\Release\net10.0-windows10.0.26100.0\win-x64'
-        $releaseExe = Join-Path $releaseDir 'AmiReel.exe'
-        $publishDir = Join-Path $releaseDir 'publish'
-        $publishExe = Join-Path $publishDir 'AmiReel.exe'
-        $publishArguments = @(
-            'publish', $projectPath,
-            '-c', 'Release',
-            '-r', 'win-x64',
-            '--self-contained', 'true',
-            '-p:WindowsPackageType=None',
-            '-p:PublishSingleFile=true',
-            '-p:IncludeNativeLibrariesForSelfExtract=true',
-            '-p:EnableCompressionInSingleFile=true'
-        )
-    }
-    'Wpf' {
-        $projectPath = Join-Path $projectDir 'AmigaDB.VideoRenderer.csproj'
-        $releaseDir = Join-Path $projectDir 'bin\Release\net8.0-windows\win-x64'
-        $releaseExe = Join-Path $releaseDir 'AmiReel.exe'
-        $publishDir = Join-Path $releaseDir 'publish'
-        $publishExe = Join-Path $publishDir 'AmiReel.exe'
-        $publishArguments = @(
-            'publish', $projectPath,
-            '-c', 'Release',
-            '-r', 'win-x64',
-            '--self-contained', 'true',
-            '-p:PublishSingleFile=true',
-            '-p:IncludeNativeLibrariesForSelfExtract=true',
-            '-p:EnableCompressionInSingleFile=true'
-        )
-    }
-}
+$projectPath = Join-Path $projectDir 'AmiReel.csproj'
+$releaseDir = Join-Path $projectDir 'bin\Release\net10.0-windows10.0.26100.0\win-x64'
+$releaseExe = Join-Path $releaseDir 'AmiReel.exe'
+$publishDir = Join-Path $releaseDir 'publish'
+$publishExe = Join-Path $publishDir 'AmiReel.exe'
+$publishArguments = @(
+    'publish', $projectPath,
+    '-c', 'Release',
+    '-r', 'win-x64',
+    '--self-contained', 'true',
+    '-p:WindowsPackageType=None',
+    '-p:PublishSingleFile=true',
+    '-p:IncludeNativeLibrariesForSelfExtract=true',
+    '-p:EnableCompressionInSingleFile=true'
+)
 
 if ((Test-Path $releaseExe) -or (Test-Path $publishExe)) {
     $runningReleaseInstances = Get-Process | Where-Object {
@@ -59,7 +36,7 @@ if ((Test-Path $releaseExe) -or (Test-Path $publishExe)) {
     }
 
     if ($runningReleaseInstances) {
-        Write-Host "Stopping running $Target build before publish..." -ForegroundColor Yellow
+        Write-Host 'Stopping running AmiReel build before publish...' -ForegroundColor Yellow
         $runningReleaseInstances | Stop-Process -Force
         Start-Sleep -Milliseconds 800
     }
@@ -71,6 +48,6 @@ if (Test-Path $publishDir) {
 
 & dotnet @publishArguments
 
-Write-Host "Published $Target to $publishDir" -ForegroundColor Green
+Write-Host "Published AmiReel to $publishDir" -ForegroundColor Green
 Write-Host "Release folder: $publishDir" -ForegroundColor Cyan
 Write-Host "Executable: $publishExe" -ForegroundColor Cyan