MCP and Behaviors: Arrange, lint_graph and the badge count (#429)

The agent gives no coordinates any more, the editor lays its nodes
out. The pages say how, and what an agent can check.

- Behaviors: the Arrange button next to the magnet, what it does
  with a selection and with groups, one undo step.
- MCP: the tool lint_graph, the command arrange_graph (24 commands
  now), nodes placed at the end of a call while placed ones stay,
  and the rule for far values.
- MCP: which agents the badge counts. Spare sessions that never
  call a tool do not.
- MCP: the tests for arrange and the new checks in e2e 71.

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

Behaviors.md

@@ -627,6 +627,13 @@ the inspector).
   switching it on never shuffles a graph that is already laid out, and a node nobody drags never
   moves. Every node of a selection snaps **for itself**, so dragging a group is how you line one
   up; the offset is a decision about rectangles and lives with the others in `editor/framing.ts`.
+- **Arrange** (next to the magnet, in every graph tab; #429) lays the graph out: the flow runs left
+  to right in columns, a node that only feeds others (a Get, the Owner) stands just left of the
+  first one it feeds, each column is put in the order that crosses the fewest links, and the nodes
+  are moved up or down towards the ports they link to without ever overlapping. With several nodes
+  selected it arranges those and leaves the rest; they keep their place if they fit there, else they
+  go right of everything. A group around them stays where it is. One undo step, *Arrange nodes*.
+  It measures every node as drawn; the rule is the pure `editor/graph/arrange.ts`.
 - **One tab per behavior**: each behavior opens as a document of its own (double-click in the
   asset panel), several at once, each keeping its zoom and scroll for the session. A selection
   never changes what a tab shows; selecting a node of another graph brings that graph's tab up.

MCP.md

@@ -19,7 +19,9 @@ clicks run. Laying out the graphs it builds comes next (see the issue).
    The server keeps only a hash of the token; close the dialog without copying it and it is gone,
    make a new one.
 2. **Switch the agent on** in the tab you want it to work in: account menu → *Agent*. A badge
-   appears beside the account menu and shows how many agents are connected. A click on the badge
+   appears beside the account menu and shows how many agents are connected: an agent counts while
+   it keeps its event stream open or has called a tool in the last two minutes. Claude Code opens
+   spare sessions when it connects, they never call a tool and do not count. A click on the badge
    switches the agent off again.
 3. Ask Claude Code about the editor. Without a tab switched on, every tool answers that no editor
    is connected and how to fix that.
@@ -57,6 +59,7 @@ the badge says *Agent offline* meanwhile.
 | `list_assets` | The assets with ids, names and types, by type or a part of the name |
 | `get_asset` | One asset as stored, with the rows of its properties and the named objects of a scene or container. A graph is only counted, pixels and map cells too |
 | `get_graph` | A graph: every node with its settings and its ports as they are now, the edges, the groups and notes |
+| `lint_graph` | How a graph reads, counted as you see it: nodes on top of each other, links that cross, links running over a node that is not theirs, links running right to left, the longest links, with a few ids of each |
 | `catalog` | What there is to make: the commands with their arguments, the nodes a graph can hold (all of them, or the best matches of a search in full), the asset types and their properties, the variable kinds |
 | `run_commands` | Changes the project, see below |
 | `open` | Brings up an asset's tab, or the scene or game tab |
@@ -83,19 +86,26 @@ it. One Ctrl+Z takes the whole call back.
   (and `"$walk.closing"` for the second node a Find adds). Each step is built after the one before
   has run, so one call can make a behavior and fill its graph.
 - **Nodes come from the palette.** `add_node` takes the id of an entry of the catalog for that
-  graph: `OnKeyHeld`, `Move`, `RunBehavior:<id>` for another behavior. Without `x` and `y` a node
-  goes right of everything the graph holds; the real layout comes with the next stage.
+  graph: `OnKeyHeld`, `Move`, `RunBehavior:<id>` for another behavior.
+- **The editor places the nodes.** Nodes added without `x` and `y` are arranged when the call has
+  run, the way the [Arrange](Behaviors) button does it, and the move is part of the same undo
+  step. Nodes that were there before stay where they are, so what you laid out by hand is never
+  shuffled; the new ones keep the place right of them. `arrange_graph` arranges nodes the agent
+  names, or the whole graph, which the agent is told to do only when you ask.
+- **Readable graphs.** The agent is told to fetch a value needed far away with a second Get or
+  Owner node next to where it is used rather than one long link, and to check with `lint_graph`.
 - **Deleting asks you.** A call that deletes an asset that was there before opens a dialog
   *The agent asks: Delete "..."?* with the same text as your own Delete. The call waits for your
   answer, up to 110 seconds; Cancel, Escape or no answer leave everything as it was.
 - **While the game runs** a change goes into the running copy, as yours would, and the answer says
   it is gone when the game stops.
 
-The 23 commands so far: assets (`create_asset`, `rename_asset`, `duplicate_asset`,
+The 24 commands so far: assets (`create_asset`, `rename_asset`, `duplicate_asset`,
 `delete_asset`, `set_asset_property`, `reset_asset_property`, `set_start_scene`), variables
 (`add_variable`, `remove_variable`, `rename_variable`), placed objects (`place_asset`,
 `remove_objects`, `move_object`, `rename_object`, `set_override`, `clear_override`, `set_parent`)
-and graphs (`add_node`, `remove_node`, `move_node`, `set_node_param`, `connect`, `disconnect`).
+and graphs (`add_node`, `arrange_graph`, `remove_node`, `move_node`, `set_node_param`, `connect`,
+`disconnect`).
 Textures, fonts, sounds and videos need a file and cannot be made by an agent.
 
 A behavior acts on the object it is placed under. The smallest walking object is therefore a
@@ -138,9 +148,14 @@ What is behind it on the server, and the routes it uses: [API](API), [Developmen
   routes as everybody, with and without the relay's key.
 - `tests/editor/agent-view.test.ts`: what `get_view` answers, its one line, the tools' arguments.
 - `tests/editor/agent-edit.test.ts`: a walking object built in one call and taken back whole by one
-  undo, a failing step that leaves nothing, argument checks, deletes that ask, the reading tools
-  and the catalog.
+  undo, a failing step that leaves nothing, argument checks, deletes that ask, nodes arranged at the
+  end of a call while placed ones stay, `arrange_graph`, the reading tools and the catalog.
+- `tests/editor/graph-arrange.test.ts`: the layout on the graph an agent really built for "walk with
+  the arrow keys" (no overlaps, no link over a node, none backwards, at most 8 crossings with one
+  Owner for four moves and 4 with one each), chains running straight, nodes that stay, groups kept
+  clear, loops, and what `lint_graph` counts.
 - e2e step 71 (`tools/e2e/71-mcp.mjs`): a token made in the dialog, the agent switched on in the
   account menu, an MCP client reading the view, hearing a tab switch and taking a screenshot; the
-  agent building a walking object that moves when played, one Ctrl+Z taking it back, a delete
-  waiting for the user's Cancel; and the badge switching it off.
+  agent building a walking object whose nodes come out arranged, Arrange in the header untangling
+  it as one undo step, the object moving when played, one Ctrl+Z taking it back, a delete waiting
+  for the user's Cancel; and the badge switching it off.