Add window-based target picker as the default; process list goes advanced

New host/src/inject/window_list.{hpp,cpp} enumerates visible, titled, non-tool
top-level (alt-tab-style) windows via EnumWindows -- root-owner only, our own
process excluded -- and maps each to its owning pid + image name. The Injection
panel now defaults to this window list (each row "title [process.exe pid]", with a
filter over title or process), since there are far fewer windows than processes and
a window maps straight to the HWND the capturer wants. The full process list stays
as the advanced picker under Debug details.

Verified live: launched the host and captured its window -- the picker lists real
windows (Discord/Firefox/Explorer/...) in "title [exe pid]" form, filter present,
and the host's own window correctly excluded. x64 build green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -75,16 +75,6 @@ is removed from this list once done — so the top item is always next. The
 self-verifiable tooling / UI / input items come first; the game-pipeline items that
 need a real game (and Remote Play) to fully validate come last.
 
-- **Select targets by window, not just process.** A flat process list is fine as an
-  advanced/debug view, but the default should be a **window list** — there are far
-  fewer top-level windows than processes, and a window directly yields the HWND the
-  WGC capturer and focus spoof already want. *How:* add a window enumerator
-  (`EnumWindows`, keeping visible, titled, non-tool top-level windows —
-  `IsWindowVisible`, `GetWindowTextLength > 0`, exclude `WS_EX_TOOLWINDOW` and our own
-  HWND, resolve to the root owner) and map each via `GetWindowThreadProcessId` → pid →
-  image name. Show **title + process name + pid** with a filter box like the process
-  list; injecting by window injects into its pid and hands the HWND straight to
-  capture. Keep the process list behind "Debug details" as the advanced path.
 - **Auto-size and lay out the overlay windows so none need manual resizing.** Panels
   currently `Begin` at default cascade positions, so they overlap and clip. Give each
   `ImGuiWindowFlags_AlwaysAutoResize` and an initial position computed from