docs: chapters also come from an episode's MP3 file

docs/src/content/docs/player.md

@@ -61,7 +61,7 @@ Except on a phone, a note that you open from the player opens next to the PodNot
 
 The full player has three panels:
 
-- **Chapters** lists the episode's chapters. It appears only when the episode's feed gives chapters.
+- **Chapters** lists the episode's chapters. It appears only when the episode has chapters.
 - **Transcript** shows the transcript that the episode's feed publishes.
 - **Up next** shows the queue.
 
@@ -71,6 +71,8 @@ In a narrow view, the panel buttons are at the bottom of the full player. Select
 
 Each chapter shows its start time and title, and the current chapter is highlighted. Select a chapter to play from its start.
 
+The chapters come from the chapters file in the episode's feed. Without one, PodNotes reads the chapters that many hosts embed in an episode's MP3 file, and it asks for only the start of the file to find them. After a restart, it waits until you select **Play**. Episodes that you play from your vault get no chapters this way.
+
 ### Read the transcript
 
 The panel loads the transcript that the episode's feed publishes. Its top line reads **Feed transcript** and **Free**.

docs/src/content/docs/templates.md

@@ -88,7 +88,7 @@ PodNotes percent-encodes URLs from a feed where they contain whitespace, control
 
 With no argument, `{{duration}}` gives `4:05` for an episode under an hour and `1:02:03` for longer ones. `{{duration:minutes}}` gives whole minutes, and `{{duration:seconds}}` gives seconds. Any other argument is a [time format](/timestamps/#time-formats), as in `{{duration:HH:mm:ss}}`. An episode restored from an older version can lack a duration. Create its note from the episode's menu on its podcast's page. That menu uses the feed's copy of the episode, so `{{duration}}` has a value when the feed gives one.
 
-`{{chapters}}` reads the chapters file from the feed's Podcasting 2.0 `<podcast:chapters>` tag. Each visible chapter becomes a line such as `- 0:00 Chapter title`, sorted by start time, with the title as plain text. PodNotes leaves out chapters marked `toc: false`. A failed request or an empty chapters file gives an empty value.
+`{{chapters}}` reads the chapters file from the feed's Podcasting 2.0 `<podcast:chapters>` tag. Without one, it reads the chapters embedded in the episode's MP3 file, for an episode streamed from a feed. Each visible chapter becomes a line such as `- 0:00 Chapter title`, sorted by start time, with the title as plain text. PodNotes leaves out chapters marked `toc: false`. A failed request or an episode without chapters gives an empty value.
 
 ### <span id="linking-an-episode-to-its-podcast-feed-note"></span>Feed link tags