feat(backdrop): Capture Window… in-app window pin (TASK 38, Good Dog ONE test)

Click-to-pin an open window as the full-bleed Live backdrop, via the existing
window:<hwnd> capture path (same render layer as game/desktop). Session-scoped:
window:/picker: keys heal to auto on reload (HWND-recycle hazard); pin wins
while the window enumerates, then auto-fallbacks (game → desktop → static); a
dead window's capture session heals to auto, no dead ends.

Fix: ScreenCaptureSourceFactory.Resolve hex-parsed "window:0x<Hwnd>" WITHOUT
stripping the 0x prefix — NumberStyles.HexNumber rejects it, so every pin
resolved null ("No capture target for this key") and the heal silently rolled
back. Same flaw in IsAliveWindowPin (pin-wins guard was dead). Both fixed.

Commit also carries an out-of-scope prerequisite: PillRadioTests.cs:105 had a
committed stray token ("...PrimaryStartButtonLabel soil;", CS1003) blocking the
whole test-project compile — token removed.

Plus the previous session's uncommitted pricing docs (one-time $29/$49) that
share TASKS.md/ai.md/HANDOFF.md.

Models/WindowInfo.cs

@@ -0,0 +1,27 @@
+namespace ytLive.Models;
+
+/// <summary>One user-visible open window offered by the "Capture Window…"
+/// submenu. Carries its owning process name for disambiguation and the raw
+/// HWND that becomes the "window:&lt;hwnd&gt;" capture key.</summary>
+public sealed class WindowInfo
+{
+    public WindowInfo(string title, string processName, long hwnd, int processId)
+    {
+        Title = title;
+        ProcessName = processName;
+        Hwnd = hwnd;
+        ProcessId = processId;
+    }
+
+    public string Title { get; }
+    public string ProcessName { get; }
+    public long Hwnd { get; }
+    public int ProcessId { get; }
+
+    /// <summary>Menu label: "Title — ProcessName" (e.g. "bash — WindowsTerminal").</summary>
+    public string Label => $"{Title} — {ProcessName}";
+
+    /// <summary>The capture key fed to the screen-capture factory
+    /// ("window:&lt;hwnd&gt;").</summary>
+    public string CaptureKey => $"window:0x{Hwnd:X}";
+}