Revert the PiP content-source switch, and add pause from anywhere

[MyNamesEMurray]

What & why

1. Revert: background streaming is broken on v1.11.3 (the urgent half)

v1.11.3 swapped the video-call content source for the sample-buffer one to get the close and restore buttons back. On a device the window then never opened at all, so background streaming was gone outright — a worse failure than the missing buttons it was meant to fix, and the one PiP failure with no symptom of its own: the stream simply ends as the app leaves the screen, exactly as it did before the feature existed.

This restores AVPictureInPictureVideoCallViewController, and with it the orientation handling that had been removed as redundant — the window is shaped and rotated to how the phone is being held, read while the app is still on screen (that fix shipped in the same release that broke the window, so it has never actually been seen working).

Two things kept from the attempt:

• failedToStartPictureInPictureWithError now logs iOS's own reason instead of silently swallowing it. That is what would have explained this in seconds rather than a release cycle.
• BackgroundPiP.swift records why this flavour is the one that works, so the swap isn't attempted blind again.

The window therefore has no buttons of its own. Stopping or pausing from outside the app goes through OBS, the web panel or Siri; the Documentation screen and troubleshooting page now say that rather than describing buttons that aren't there.

2. Pause, from any surface — and a paused stream that looks paused

New CONTROL commands pause_stream / resume_stream hold a running stream instead of ending it: the app keeps the connection, the camera and the encoder, and stops sending video. Resuming asks for a keyframe, so OBS has something self-contained to restart on. Audio is deliberately untouched — a phone doubling as the wireless mic shouldn't go silent because the picture is held. Buttons are on the Live screen (next to Stop), in the source properties, and in the web panel, all reading the same STATE so pressing one updates the others. They need no remote-start permission, since they can only hold a stream the user already started.

An async source keeps its last frame, so a pause was indistinguishable from a stall. The decoder now keeps a 64×36 luma thumbnail of the last frame — sampled sparsely, so it costs the same at 4K as at 720p and never touches chroma — and pausing blows it back up to frame size. The upscale is the blur: no kernel, no per-frame work, grey with a pause glyph over it. One frame, pushed once. The GPU pipeline keeps frames in textures with no thumbnail to sample, so there the picture stays as it was.

That also covers the PiP case: when a parked window loses the camera, STATE says paused with reason camera, so OBS shows the still instead of a frozen frame, while the app's status keeps the sentence explaining what to do. The Live screen hides its resume button there, since nothing it could press would resume anything.

Docs: PROTOCOL gains the commands and STATE fields, UI_DESIGN gains the Paused status word, and the Documentation screen plus the settings, web-panel and troubleshooting pages describe the buttons and the still.

How it was tested

• ios-app/syntax-check.sh — parses clean; site/build.py + check-links.py — 16 pages, 0 broken links.
• The three OBS plugin jobs passed on the pause work's first run, which is the only compiler that sees paused-still.c and the decoder thumbnail (no libobs in the dev container).
• Not device-tested. The revert restores code that demonstrably worked in v1.11.2, so the first thing to confirm is simply that the PiP window opens again. Then: the window's shape follows the phone's orientation (portrait and landscape), pause from each of the three surfaces shows the blurred still in OBS, resume returns to live promptly, and audio keeps flowing while paused.

Release-Bump: minor

🤖 Generated with Claude Code

https://claude.ai/code/session_01C83kP6jfQWe7dwrjB4KMPB

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