Describe the magnet of the song routing (#350)

- Songs: the routing snaps with the magnet next to Routing, which is
  greyed out on the timeline. The old line promised a snap that was
  never built.
- Development: 1890 checks.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Development.md

@@ -19,7 +19,7 @@ php tests/php/accounts.test.php                               # the API's accoun
 php tests/php/snapshots.test.php                              # the snapshot store (#231), the same way
 php tests/php/releases.test.php                               # the release store (#266), the same way
 php tests/php/files.test.php                                  # uploaded files in a folder per account (#344), the same way
-node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1889 editor checks, screenshots in /tmp/gm-e2e-*.png
+node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1890 editor checks, screenshots in /tmp/gm-e2e-*.png
 GM_STEPS=20 node tools/e2e.mjs                                # or 1-12, or 6,20 — a subset while working on one step
 ./e2e.sh start [GM_STEPS]                                     # the same run detached, see below
 ./e2e.sh status                                               # live progress, or the last run's result

Songs.md

@@ -129,7 +129,9 @@ down and the last up to half the height up; nothing lies above or below them. **
 **Routing** in the header shows the song as a graph instead of the timeline (#350): a node for
 every track, named after it, and one node **Output**. The output is what the song sounds like; from
 there it goes on to the [bus](Sounds#buses-and-the-master) of the song. It is the same graph editor
-as for a sound FX, with zoom, snap, undo, groups and comments. **Timeline** goes back.
+as for a sound FX, with zoom, undo, groups and comments. The magnet next to **Routing** snaps the
+nodes to the grid while it is lit. It is off at first and greyed out on the timeline, just as
+**Grid** is greyed out in the routing. **Timeline** goes back.
 
 - **A link is a send.** A track takes in any number of links and sends to any number of tracks and
   the output. It mixes its own items and everything that comes in, sends that through its sound FX,