Feature history on the left side, with contiguous folders (#449)

The feature history can sit in a panel on the left, with folders that hold one unbroken run of features, drag and drop as one undo step, and a resizable divider. Timeline folders save under format 17.

docs/features.md

@@ -1,6 +1,6 @@
 # Features
 
-SolidCraft's commands by area, generated by `cargo xtask features` from the command registry (`solidcraft-cli commands`). **328 commands.** Every command runs the same way from the toolbar, a script, `solidcraft-cli exec <id> '<json>'`, the control channel and MCP; parameters are in the [command reference](book/src/reference/commands.md) (`cargo xtask book`). Status and plans: [ROADMAP](../ROADMAP.md).
+SolidCraft's commands by area, generated by `cargo xtask features` from the command registry (`solidcraft-cli commands`). **335 commands.** Every command runs the same way from the toolbar, a script, `solidcraft-cli exec <id> '<json>'`, the control channel and MCP; parameters are in the [command reference](book/src/reference/commands.md) (`cargo xtask book`). Status and plans: [ROADMAP](../ROADMAP.md).
 
 ## Sketch (98)
 
@@ -257,16 +257,22 @@ SolidCraft's commands by area, generated by `cargo xtask features` from the comm
 | Configuration Rule | `config.rule` | – |
 | Configuration Rules | `config.rules` | – |
 
-## Timeline (13)
+## Timeline (19)
 
 | Command | Id | Toolbar |
 |---|---|---|
 | Compute All | `timeline.compute_all` | SOLID › MODIFY |
 | Delete (Delete) | `timeline.delete` | SOLID › MODIFY |
 | Rename | `timeline.rename` | – |
+| New Feature Folder | `timeline.group` | – |
+| Remove Feature Folders | `timeline.ungroup` | – |
+| Rename Feature Folder | `timeline.rename_group` | – |
+| Move Features to Folder | `timeline.move_to_group` | – |
+| Move Timeline Items | `timeline.move_many` | – |
 | Move Timeline Marker | `timeline.rollback` | – |
 | Roll History Marker | `timeline.roll_to` | – |
 | Reorder Feature | `timeline.reorder` | – |
+| Reorder Features | `timeline.reorder_many` | – |
 | Edit Feature | `timeline.redefine` | – |
 | Feature Dependents | `timeline.dependents` | – |
 | Suppress Feature | `timeline.suppress` | – |