Add Picture-in-Picture mode for the player

[Omurshid]

Summary

Adds a Chrome-extension-style Picture-in-Picture mode: a floating, always-on-top window that detaches the MPV video from the main window so playback continues while you browse the catalog. The same MPV instance is reparented (SetParent, no re-buffering) into the PiP window and returned to the main window on exit.

Features

• Floating PiP window — borderless, draggable, and resizable; stays on top of other apps. Position/size are persisted across sessions.
• Glass controls overlay — a custom GDI+ overlay (restore, close, play/pause, skip, seek slider, transparency toggle) that auto-hides shortly after the cursor leaves the window. Drawn as individual rounded "pills" via a window region so the video shows through the gaps.
• Transparency toggle — flips the PiP window to ~60% opacity (WS_EX_LAYERED) so you can see content behind it; the state is remembered.
• Native PiP button — injected into the web player controls by cloning Stremio's own fullscreen button, so it inherits the exact styling and auto-hide behavior. Also available from the system-tray menu.

How it works

The toggle is plumbed through the existing web↔shell IPC, mirroring the fullscreen flow:
win-set-pip (web → shell) triggers a notice handled on the UI thread; state is broadcast back with win-pip-changed. Entering PiP locates MPV's child render window and reparents it into the floating window; exiting reparents it back and re-fits the WebView.

New files

• src/stremio_app/pip_window.rs — the floating window, GDI+ overlay, drag/resize, transparency, MPV reparenting.
• src/stremio_app/mpv_hwnd.rs — locates MPV's child render window.

Notes

• Windows-only, consistent with the rest of the shell.
• cargo build, cargo clippy, and cargo test are all clean (0 warnings).

🤖 Generated with Claude Code

[kKaskak]

i do not have the capacity to review this claude generated 1700 lines of code pr im sorry

[DavidAGInnovation]

I reviewed this implementation and opened a focused alternative in #92.

The main review concerns are:

• the PR injects its own PiP control even though stremio-web#1354 owns the web control and IPC contract;
• the custom GDI+ overlay makes the change roughly 1,700 lines and duplicates player controls;
• the MPV lookup falls back to the first non-WebView child, which can select the wrong window;
• the current PR is merge-conflicting.

#92 keeps the native shell responsibility focused: it handles the IPC, reparents the existing MPV child, resizes it with the PiP window, restores it on close, and persists placement.