Describe the 1/16 grid and how new assets are routed (#365)

- Songs: a new song snaps to 1/16, Bar stays a choice.
- Sounds: a new or duplicated asset takes the links most others of
  its type have. A new bus goes to the master.
- Development: 1910 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                 # 1909 editor checks, screenshots in /tmp/gm-e2e-*.png
+node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1910 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

@@ -15,7 +15,7 @@ inspector.
 |---|---|
 | **Tempo (BPM)** | 20 to 400, quarter notes a minute. The song plays every pattern at this tempo; the tempo set on a pattern is only for its own tab. |
 | **Sign** | The time signature of the ruler (#363): 1/2, 2/2, 3/2, 1/4 to 6/4, or 5/8 to 9/8, 4/4 by default. Items are kept in ticks, so a change only moves the bar lines. |
-| **Grid** | What items snap to: **Bar** (the default), or one of the grids of a pattern, 1/1 to 1/32 and the triplets. The tab's header has the same choice. |
+| **Grid** | What items snap to: **Bar**, or one of the grids of a pattern, 1/1 to 1/32 and the triplets. A new song snaps to **1/16** (#365). The tab's header has the same choice. |
 | **Sound FX** | A [sound FX](Sounds#the-sound-fx-of-an-asset) the whole song goes through, after its tracks and the routing, before its links in the Master routing (#352). `Play song` and the tab play through it. |
 
 Where a `Play song` and the tab are heard is said by the links of the song's node in the

Sounds.md

@@ -269,9 +269,15 @@ master goes straight out.
 
 - **A node per asset.** Every sound, instrument, pattern, song and bus of the project has one,
   named after it, and there is one **Master**. The nodes come and go with the assets: a new asset
-  gets its node in a column for its type, linked to the master, and a deleted one takes its node
-  and its links along. They cannot be added or deleted by hand. What a song keeps to itself
-  (an embedded sound or pattern) has no node: its song routes it.
+  gets its node in a column for its type, and a deleted one takes its node and its links along.
+  They cannot be added or deleted by hand. What a song keeps to itself (an embedded sound or
+  pattern) has no node: its song routes it.
+- **A new or duplicated asset goes where the others go** (#365). A sound, instrument, pattern or
+  song gets the links most others of its type have, at their volume: with two sounds in *SFX* and
+  *Reverb* and one on the master, the next one goes into *SFX* and *Reverb*. On a tie the latest
+  of them decides, so if there is only one song, the next one follows it. Where nothing of its
+  type is linked yet, it goes as most of all that plays, and where nothing is, to the master.
+  A new bus is always linked to the master.
 - **Links are sends.** A drag from the out of a node into the in of a bus or of the master links
   them. A node may have several links, the same sound then goes everywhere it is linked at once:
   a step sound into *SFX* and, quieter, into a *Reverb* bus. Only a bus and the master take links