docs(user): koreader install is a git clone (git pull to update), per owner

Replaced the 'clone then copy to plugins/' phrasing with the actual
workflow: clone straight into the plugins folder (koreader/plugins,
.adds/koreader/plugins on Kobo), restart KOReader; updates are git pull
in bookhoard.koplugin + restart. Closes the last prose-trusted item in
the user-docs rebuild.

docs/user/devices/koreader-setup.md

@@ -80,9 +80,18 @@ web interface — no usernames, passwords, or tokens to type on the device.
 
 ### Step 1: Install the Bookhoard Plugin
 
-1. Clone the [Bookhoard KOReader plugin](https://git.linuxhg.com/Bookhoard/bookhoard.koplugin)
-2. Copy it to your KOReader `plugins/` directory
-3. Restart KOReader
+Installation is a git clone straight into your KOReader `plugins/` folder —
+no download-and-copy step:
+
+```bash
+cd koreader/plugins        # .adds/koreader/plugins on Kobo
+git clone https://git.linuxhg.com/Bookhoard/bookhoard.koplugin
+```
+
+Then restart KOReader.
+
+**Updating later** is the same, smaller: in the `bookhoard.koplugin` folder,
+`git pull`, then restart KOReader.
 
 ### Step 2: Point the Plugin at Your Server