GetWindowTitle was returning info.Name (the window's identifier) instead
of the actual title. Added Title() to the PlatformWindow interface and
Title field to WindowInfo so the real title flows through queries.
Added wsRequire() helper and input validation for all webview:* WS
message cases — window name is required for every webview action, and
selectors/URLs are validated where they'd cause errors if empty.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Adds OnFileDrop(handler func(paths []string, targetID string)) to PlatformWindow.
trackWindow() now wires file drop callbacks to ActionFilesDropped broadcasts.
Updates both exported MockWindow and unexported mockWindow with the new method.
Wails adapter maps WindowFilesDropped event with DroppedFiles and DropTargetDetails.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
