Let the agent use the graph, scene and project commands (#429)

The agent knew 23 of the editor's commands. It could not point a
Variables node at a variable, group nodes, edit ports, transitions,
containers, colliders or the project settings. Stage 5a brings the
catalog to 85 commands in five areas and keeps every answer short.

- The catalog lists names and descriptions only. With a query (an
  area or command names) it adds the arguments. All schemas at once
  would pass the 60 000 character limit of one answer.
- add_port points a Variables node at a variable. The port takes the
  variable's kind, and an unknown name is refused with the list of
  the ones that exist.
- add_group and add_comment take nodes instead of coordinates. They
  follow the nodes after the arrange step, in the same undo step.
- The rule for which list a port picks from moved into portChoices.ts.
  Inspector and agent now share it.
- The frame of a group around nodes moved into annotationDrag.ts, so
  the button and the agent get the same frame.
- list_assets returns the project settings. get_asset shows the
  content of placed containers with the ids overrides need. get_graph
  shows declared ports and frame colors.
- A new node is placed at the height of its port, in the free spot
  whose links cross the fewest others. A source goes left of the node
  it feeds. Before, new nodes always went right of the rest.
- Arrange breaks a tie in crossings by putting the flow on top, and
  exec links pull harder when a column is sorted.
- A comment over a group keeps clear of the group's title bar.
- The agent's instructions and lint_graph ask to look at crossings
  too and to call arrange_graph when there are more than needed.

Left out on purpose: file assets (no upload), paste from the
clipboard, internal wrapper commands and switching plugins on.

Found on the way:
- Variable commands on a Struct asset did not run through
  WithStructTypes. New fields did not reach variables of that type.
- A query "variables" also matched set_variables_scope. A word that
  names an area now means only that area.

Tests:
- agent-catalog (new, 10), agent-edit, graph-arrange (3 new) and
  relay green. 11 bends of the code, all red.
- e2e 71 on atx: 22/22, the new check sees port speed and a group
  around all 4 drawn nodes.
- Live on a test project: a speed variable of 300 moved the player
  to x 150.03 in 0.5 s. A re-placed Variables node landed below Axis
  input with 4 crossings instead of 7.

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

tools/mcp/relay.mjs

@@ -35,12 +35,16 @@ const INSTRUCTIONS = [
   'live: the user sees every change you make and can take it back with Ctrl+Z.',
   'Start with get_view to learn what the user is looking at; screenshot shows it as a picture.',
   'Read the project with list_assets, get_asset and get_graph. Change it with run_commands: its steps',
-  'are commands from catalog topic "commands", run as one undo step, and a step can name what an',
-  'earlier one made ("as": "x", then "$x"). Nodes for a graph come from catalog topic "nodes".',
-  'A behavior acts on the object it is placed under: place it with parent set to that object.',
+  'are commands from catalog topic "commands" (by area; ask with query for their arguments), run as',
+  'one undo step, and a step can name what an earlier one made ("as": "x", then "$x"). Nodes for a',
+  'graph come from catalog topic "nodes". A Variables node reads or writes a variable once add_port',
+  'names it. A behavior acts on the object it is placed under: place it with parent set to that object.',
   'Give new nodes no x and y: the editor arranges them when the call ends, and leaves the nodes',
   'already there where they are. Keep a graph readable: a value needed far away comes from a second',
-  'Get or Owner node next to its user, not over a long link; check with lint_graph.',
+  'Get or Owner node next to its user, not over a long link. Check with lint_graph, the crossings',
+  'too: when there are more than the links need, arrange_graph orders the whole graph for the',
+  'fewest. Put nodes that belong together into a group with add_group, and say what they do with',
+  'add_comment.',
   'The editor follows your edits: after run_commands the user sees the graph, scene or asset it worked',
   'on, with what it touched selected. Use open and select to show anything else.',
   'Test what you built yourself: play, then play_input sends keys and mouse clicks into the game,',