Blob Brush: Keep selected and Merge only with selection options

A Blob Brush stroke merged with every touching closed path of its
color that had no stroke, and the blob it drew or merged into was
always left selected. The Blob Brush Tool Options had Size only.

The Blob Brush Tool Options now have Keep selected and Merge only
with selection, both off by default. A blob that a stroke draws or
merges into is no longer left selected unless Keep selected is on,
and the rest of the selection stays as it was. While Merge only with
selection is on, a stroke merges only with selected blobs, and with
nothing selected it draws a new blob. The options persist like the
tool's Size, and path.blob takes keepSelected and mergeOnlySelection,
both false by default. Keep selected stays on by default for the
Pencil and Paintbrush.

Docs: docs/target-app-parity.md, docs/control-protocol.md.

docs/control-protocol.md

@@ -764,9 +764,11 @@ events take `pressure` (0..1, default 1): it is the Liquify intensity while Use
 
 Freehand Tool Options: double-clicking the Pencil, Paintbrush, Smooth, Blob Brush or Eraser tool
 (`tool.options {tool: "pencil"}`) opens a `freehandOptions` dialog. Its fields are `tool` and the options the tool
-keeps: `fidelity` (pt; Pencil, Paintbrush, Smooth), `fill` and `keepSelected` (Pencil, Paintbrush; `keepSelected`
-is on by default, and while it is off the path a stroke draws or continues is not selected afterwards), `closeWithin`
-and `editWithin` (screen pixels, 0 turns it off; Pencil, Paintbrush) and `size` (pt; Blob Brush, Eraser). `ui.dialog.confirm` runs
+keeps: `fidelity` (pt; Pencil, Paintbrush, Smooth), `fill` (Pencil, Paintbrush), `keepSelected` (Pencil, Paintbrush,
+Blob Brush; on by default for the Pencil and Paintbrush and off for the Blob Brush, and while it is off the path a
+stroke draws, continues or merges into is not selected afterwards), `mergeOnlySelection` (Blob Brush; off by default,
+and while it is on a stroke merges only with selected blobs), `closeWithin` and `editWithin` (screen pixels, 0 turns
+it off; Pencil, Paintbrush) and `size` (pt; Blob Brush, Eraser). `ui.dialog.confirm` runs
 `tool.setOption {tool, values}`.
 
 `ui.pointer` events also take `holdMs` (0..60000): the pointer then holds still that long, button down, before the

docs/target-app-parity.md

@@ -498,6 +498,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
     In the Swatches panel, Alt-dragging a swatch onto another swatch of its kind (not a tint swatch) replaces that swatch's color, gradient or pattern, and the swatch keeps its name and place.
   - **Tool double-clicks:** double-clicking a tool's button opens its options: Hand fits the artboard in the window, Zoom shows 100 %, Rotate, Scale, Reflect and Shear open their Object › Transform dialogs, the Selection, Direct Selection and Group Selection tools the Move dialog (Enter opens these seven tools' dialogs too), Gradient, Eyedropper, Blend and the Liquify tools their panels or options, the Pencil, Paintbrush, Smooth, Blob Brush and Eraser tools their Tool Options (Fidelity, fill, Keep selected, the tolerances, the brush size), and (#812) the Flare tool its Flare Tool Options, the Artboard tool the active artboard's Artboard Options, the graph tools Graph Type for the selected graph, the Symbolism tools the Symbolism Tools Options (Diameter, Intensity, Symbol Set Density) and the Magic Wand tool its panel.
     Keep selected in the Pencil and Paintbrush Tool Options is on by default; while it is off, the path a stroke draws or continues is not selected afterwards and the rest of the selection stays as it was (`path.freehand` `keepSelected`).
+    The Blob Brush Tool Options have Keep selected and Merge only with selection, both off by default: while Keep selected is off, the blob a stroke draws or merges into is not selected afterwards, and while Merge only with selection is on, a stroke merges only with selected blobs of its color that it touches (`path.blob` `keepSelected` and `mergeOnlySelection`).
 - **Ruler guides as layer objects:** a guide goes on the current layer, shows, hides, locks and is deleted with it, is listed in the Layers panel (its row selects it) and moves to another layer (`guide.setLayer`, or its row dragged onto that layer's rows); guides on a hidden or locked layer can't be selected, moved or deleted, Duplicate copies a layer's guides and Merge Selected and Flatten Artwork keep them on the merged layer; guides from files saved before guides had layers go on the top visible, unlocked layer when the document opens. Not done: guides stacked among the art of their layer (they are listed above it), a guide row's own eye and lock. Lock Guides also locks the objects made into guides: they can't be selected, moved or deleted (#1543); they are drawn in the guide colour and style of Preferences, and a dragged selection snaps to ruler guides with Smart Guides on (#1583, fixes #1534). The Transform panel shows a selected ruler guide's X or Y, and typing a value moves it (#1659, part of #1597). This is not established by the documentation we could find: the public help pages on guides, rulers and the Transform, Control and Properties panels (read again on 2026-10-14) describe selecting and dragging unlocked guides and the panels' X and Y for a selection, not a guide's position in a panel, and the one public statement of it is a user's [community answer](https://community.adobe.com/questions-652/adding-a-new-custom-guide-785586), which is not documentation. It is kept as a convenience pending the owner's decision, with no parity claim and nothing counted towards a score.
 - **Layers panel:** every layer, sublayer, group and object is a clickable row at any depth: a click highlights it and makes its layer current (new art goes there), Shift-click a range, Ctrl/Cmd-click toggles. Sublayers are no longer treated as objects: clicks, marquees, Select All and the Select menu take the art inside them, and each sublayer selects in its own colour. Selection squares on rows with selected art (click selects a row's art, Shift adds or removes; dragging the square moves the selection to another row, Alt copies), the eye and lock on every row with drag-down-the-column (one undo step), Ctrl/Cmd-click an eye for per-layer Outline, Alt-click an eye or lock to hide or lock the other layers (again: show or unlock them all), triangles with Alt to open or close everything inside, drag and drop rows above, below or into layers and groups with a drop line (Alt copies) and a dimmed copy of the row under the pointer (dropped on the trash rows are deleted, on New Layer duplicated, as in Illustrator), inline rename, Delete key on highlighted rows. Buttons and the full panel menu: New Layer/Sublayer (Alt: options, Ctrl: on top), Duplicate, Delete, Options for Selection, clipping mask, isolation, Locate Object, Merge Selected, Flatten Artwork, Collect in New Layer, Release to Layers (Sequence and Build), Reverse Order, Template, Hide/Outline/Lock Others and Show/Preview/Unlock All, Paste Remembers Layers, Panel Options (row size, thumbnails per kind, Show Layers Only). Layer Options: name, colour (presets, each with a chip of its colour, or custom), Template, Lock, Show, Print, Preview (outline drawing and clicking) and Dim Images to %. Every operation is a command (`layer.move`, `layer.highlight`, `layer.merge`…) with validation against cycles and invalid nesting. A document opens with only its top-level layers open; the rows left open are saved in the native file (nothing is written for the default) and reopen that way. Only the rows scrolled into view are laid out, from a row list made once per change: a layer of 5,000 groups of 10 paths, all open, draws the panel in 0.4 ms a frame instead of about 29 s (#638).
   The Filter button at the right of Search All keeps the rows that are of an object kind ticked under By Object (paths, shapes, text, images, effects, groups, linked files, guides) and in a state ticked under By Layer (locked, hidden), with the rows that hold them; a section with nothing ticked takes every row. The filter combines with the search, the button is lit while a filter is on, and Clear All in its popup turns the filter off (`ui.layersFilter`). The filter lasts the session.