Fix smoke 2차 gaps: hotkey tests, focus filter, viewport picking (#13)

Gap E — Hotkey named key
- UiaPlayerHost: extract ParsedHotkey record + ParseHotkey static
- HotkeyParseTests: 8 tests (enter/tab/a/ctrl+c/ctrl+shift+s/f5/alt+f4/empty)

Gap F — recorder focus_change SUT filter
- FocusEventFilter.ShouldAccept static rule (same/zero/unknown/unknown-sut)
- Program.cs wires it inside RegisterFocusChangedEvent callback
- FocusEventFilterTests: 4 tests

Gap G — viewport picking foreign-process fallback
- IWindowPointSource + WindowPointResolver pure resolver
- FlaUiPointSource wired in Program.cs (best-effort hit test, honest partial for live SUT)
- WindowPointResolverTests: 5 tests

Tests: 77 → 94, build 0/0 (TreatWarningsAsErrors preserved).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/Recordingtest.Player/Recordingtest.Player.csproj

@@ -12,4 +12,7 @@
     <PackageReference Include="FlaUI.UIA3" Version="4.0.0" />
     <PackageReference Include="YamlDotNet" Version="16.1.3" />
   </ItemGroup>
+  <ItemGroup>
+    <InternalsVisibleTo Include="Recordingtest.Player.Tests" />
+  </ItemGroup>
 </Project>

src/Recordingtest.Player/UiaPlayerHost.cs

@@ -77,9 +77,10 @@ public sealed class UiaPlayerHost : IPlayerHost, IDisposable
             new System.Drawing.Point(from.X, from.Y),
             new System.Drawing.Point(to.X, to.Y));
 
-    public void Hotkey(string keys)
+    internal sealed record ParsedHotkey(IReadOnlyList<VirtualKeyShort> Modifiers, VirtualKeyShort? Main);
+
+    internal static ParsedHotkey ParseHotkey(string keys)
     {
-        // Minimal: support "ctrl+s" style.
         var parts = keys.Split('+', StringSplitOptions.RemoveEmptyEntries);
         var modifiers = new List<VirtualKeyShort>();
         VirtualKeyShort? main = null;
@@ -120,9 +121,15 @@ public sealed class UiaPlayerHost : IPlayerHost, IDisposable
                     break;
             }
         }
-        foreach (var m in modifiers) Keyboard.Press(m);
-        if (main is not null) Keyboard.Type(main.Value);
-        foreach (var m in modifiers) Keyboard.Release(m);
+        return new ParsedHotkey(modifiers, main);
+    }
+
+    public void Hotkey(string keys)
+    {
+        var parsed = ParseHotkey(keys);
+        foreach (var m in parsed.Modifiers) Keyboard.Press(m);
+        if (parsed.Main is not null) Keyboard.Type(parsed.Main.Value);
+        foreach (var m in parsed.Modifiers) Keyboard.Release(m);
     }
 
     public void CaptureCheckpoint(int afterStep, string saveAs)