Clarify which rooms can be forwarded into a composition

docs/explanation/compositions.mdx

@@ -18,7 +18,7 @@ Compositions are built on [Smelter](https://smelter.dev), the source-available r
 
 ## What you can build
 
-- **Multi-party layouts**: arrange the cameras of a conference or livestream into grids, side-by-sides, or picture-in-picture.
+- **Multi-party layouts**: arrange the cameras of a conference room, or several independent streams, into grids, side-by-sides, or picture-in-picture.
 - **Branded streams**: overlay logos, captions, lower-thirds, and backgrounds on top of live video.
 - **Cross-protocol bridging**: take WebRTC inputs and republish the composed result over RTMP, for example broadcasting a conference to YouTube or Twitch, or the other way round.
 - **Recordings**: capture the composed stream as an MP4 file to store, replay, or serve on demand.
@@ -35,6 +35,13 @@ A composition produces video, it does not serve it. There is nowhere to point a
 
 An output's scene can either be described directly in the API or rendered by a **template**: a React component, written with the layout components and the [`@fishjam-cloud/composition`](./../how-to/compositions/write-and-deploy-a-template) hooks, that updates the layout live as the room changes.
 
+## Getting media in
+
+There are two ways to feed a composition:
+
+- **Publish straight to an input.** Register an input and point any source at it: OBS, a phone camera, a browser tab, an RTMP encoder, or an MP4 file. This is the simplest path and needs no room. See [Choose inputs and outputs](./../how-to/compositions/inputs-and-outputs).
+- **Forward a Fishjam room.** Use this to compose every peer of a [conference or audio-only room](./rooms). Fishjam registers an input per participant and keeps them in sync as peers join and leave. Livestream rooms cannot be forwarded. See [Compose a Fishjam room](./../how-to/compositions/compose-a-fishjam-room).
+
 ## Cost and lifecycle
 
 A running composition holds a live rendering session for as long as it exists, and you are billed for that time whether or not anyone is watching.

docs/how-to/compositions/compose-a-fishjam-room.mdx

@@ -1,6 +1,6 @@
 ---
 type: how-to
-sidebar_position: 2
+sidebar_position: 3
 description: Forward a Fishjam room into a composition and render its peers with a live React template.
 ---
 
@@ -16,6 +16,12 @@ A composition can include the peers of a [Fishjam room](./../../explanation/room
 Fishjam room (peers) ──forwarded──▶ composition (template) ──WHIP──▶ Fishjam livestream ──WHEP──▶ [viewers]
 ```
 
+:::note
+Only [conference](./../../explanation/rooms#conference-rooms-default) and [audio-only](./../../explanation/rooms#audio-only-rooms) rooms can be forwarded. Forwarding a [livestream room](./../../explanation/rooms#livestream-rooms) fails.
+
+To compose a single stream, such as OBS, a phone camera, or a browser tab, you don't need a room at all. Publish it straight into the composition through a [`whip_server` input](./inputs-and-outputs#inputs).
+:::
+
 ## Prerequisites
 
 - A [livestream](./../../explanation/livestreams) (or any other WHIP/RTMP destination) to publish the composed stream to.

docs/how-to/compositions/drive-a-template-with-events.mdx

@@ -1,6 +1,6 @@
 ---
 type: how-to
-sidebar_position: 3
+sidebar_position: 4
 description: Send custom events to a running composition to update a template's on-screen state at runtime.
 ---
 

docs/how-to/compositions/inputs-and-outputs.mdx

@@ -1,6 +1,6 @@
 ---
 type: how-to
-sidebar_position: 4
+sidebar_position: 1
 description: Choose the right input and output protocols for a composition, from WebRTC to RTMP and MP4.
 ---
 

docs/how-to/compositions/write-and-deploy-a-template.mdx

@@ -1,6 +1,6 @@
 ---
 type: how-to
-sidebar_position: 1
+sidebar_position: 2
 description: Write a React composition template, bundle it with the CLI, and deploy it as an output.
 ---