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

docs/PERFORMANCE.md

@@ -40,16 +40,12 @@ should add as close to zero as possible.
   cover (`CameraPreviewView.previewEnabled`). The outgoing stream is
   unaffected. On top of the existing OLED-black + brightness drop, this
   is the biggest saver for the "phone mounted behind the monitor" case.
-- **Background PiP feeds a 1-point layer while armed, and nothing when
-  it isn't.** `BackgroundPiP.enqueue` returns on a lock-guarded flag
-  whenever background streaming is off or nothing is streaming. While a
-  stream *is* armed for PiP the layer is fed continuously, even before a
-  window opens — PiP adopts a layer that is already showing something,
-  and a layer fed nothing has nothing to hand over — so the cost is one
-  `enqueue` into a one-point display layer per frame. The buffers are
-  the ones the encoder already has (no second capture, no second
-  composite), and frames the layer isn't ready for are dropped rather
-  than queued.
+- **Background PiP costs one boolean read per frame while inline.** The
+  frame tee into the PiP window (`BackgroundPiP.enqueue`) returns on a
+  lock-guarded flag until a window is actually open, so the on-screen
+  path is unchanged; once open, the window is fed the buffers the
+  encoder already has (no second capture, no second composite) and drops
+  frames the display layer isn't ready for rather than queueing them.
 - Idle standby listener costs nothing measurable: no timers, no camera —
   just an accepting socket and 1 Hz timesync replies while OBS is
   connected.

docs/PROTOCOL.md

@@ -120,6 +120,8 @@ Camera remote control. Payload: UTF-8 JSON, one command per packet:
 { "cmd": "exposure", "mode": "auto" }
 { "cmd": "start_stream" }
 { "cmd": "stop_stream" }
+{ "cmd": "pause_stream" }
+{ "cmd": "resume_stream" }
 { "cmd": "set_format", "resolution": "1080p", "fps": 60, "codec": "hevc" }
 { "cmd": "mic", "id": "builtin:2" }
 { "cmd": "tally", "program": true, "preview": false, "sync": "locked" }
@@ -189,6 +191,15 @@ Camera connections only; screen mirror ignores it.
 Unknown commands are ignored, so new ones can be added compatibly. The
 plugin's embedded web panel (http://localhost:9980) generates these.
 
+`pause_stream` / `resume_stream` **hold** a running stream instead of
+ending it: the app keeps the connection, the camera and the encoder, and
+simply stops sending VIDEO. Audio is unaffected — a phone acting as the
+wireless mic keeps carrying the show. Resuming asks the encoder for a
+keyframe, so the plugin has something self-contained to restart decoding
+on. Unlike remote start these need no **Remote start from OBS**
+permission: they can only hold a stream the user already started, never
+turn a camera on.
+
 `start_stream` / `stop_stream` are the **remote start** commands: they
 start/stop the camera itself (not just the connection) and are honoured
 only while the app's **Remote start from OBS** option is on. The plugin
@@ -229,6 +240,14 @@ H.264 through the ordinary `set_format` validation. Both fields are
 absent on SDR streams, whose snapshots are unchanged from before
 colour modes existed.
 
+Pause rides the snapshot too: `"paused": true` while video is held, with
+`"pauseReason"` saying who held it — `"user"` for an operator pause (the
+app's Pause button, the web panel, or the source properties) or
+`"camera"` when iOS took the camera away, which happens when a PiP
+window carrying a background stream is parked at the screen edge. The
+reason is what lets a surface choose between offering a Resume button
+and explaining that the phone is waiting on iOS.
+
 Green screen state rides the snapshot the same way:
 `"supportsGreenScreen": true` advertises the feature (remote UIs gate
 their row on it), `"greenScreen": true` appears while it is armed,

docs/UI_DESIGN.md

@@ -52,8 +52,18 @@ colours so it also looks native on the phone.
 | Standby      | `connectAmber`| `#FF9F0A` | "OBS connected — ready" |
 | Connecting   | `connectAmber`| `#FF9F0A` | "Waiting for OBS…" |
 | Live         | `liveGreen`   | `#30D158` | "Live"           |
+| Paused       | `connectAmber`| `#FF9F0A` | "Paused"         |
 | Error        | `errorRed`    | `#FF453A` | *(the message)*  |
 
+Paused is a **held** stream, not a broken one: connected, camera
+running, no video going out. It takes the same amber as Standby and
+Connecting — connected but not live — and is always the single word
+"Paused". An operator pause (the Live screen's pause chip, the web
+panel, the source properties) says exactly that; a pause iOS forced by
+taking the camera keeps its explanatory message instead, because there
+the sentence is the actionable part. Either way the plugin learns of it
+through STATE and says so rather than sitting on a frozen picture.
+
 Standby is the remote-start state: the app is idle but OBS is connected
 and can start the camera. It shares the amber of Connecting — both mean
 "linked, not yet live". On the web panel the standby state replaces the