Consolidate duplicated editor code, trim comments, refresh README

Split GraphCanvas (1076 -> 831 lines) into EdgeLayer and graphMenus;
the port and marker menus were the same list and are now one function.
Value specs of the inspector and the list tab share valueSpecs.ts, and
the remaining copies (compound commands, type glyphs, typed asset
lookup, name rule, play/editor world setup, marquee) are merged.

Four copies had already drifted apart; merging them fixes:
- "Disconnect N links" in the port menu is one undo step, not N
- "+ Add collider" is hidden on a placed container instance, as in
  the hierarchy menu, instead of always failing
- a bool property coerced from the text "false" becomes false
- a port command on an unknown node type reports instead of crashing

Comment-only edits leave the bundle byte-identical. README corrected in
35 places (step limit, jump-run clock, suite duration, 409 body, ...).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/editor/inspector/objectSection.ts

@@ -38,14 +38,15 @@ import {
   resolveSceneObjectProps,
 } from '../../core/properties/resolve';
 import { Button, TextField } from '../../ui';
-import { addCollider, createContainer, removeObjects } from '../actions';
+import { addCollider, canAddCollider, createContainer, removeObjects } from '../actions';
 import { aspectActions, sizeCommand } from './aspectAction';
 import { defSignature } from './assetSection';
 import { createFieldRow, type FieldRow, labelledRow, type RowActions } from './fieldFactory';
 import { addGap, addNote, addTitle, type InspectorHost } from './host';
 import type { ListSlot } from '../state';
 import { parentRow } from './parentRow';
-import { listOpener, type PreviewedValue, previewingHandlers, structFields } from './previewHandlers';
+import { listOpener, previewingHandlers, structFields } from './previewHandlers';
+import { overrideValue } from './valueSpecs';
 import { buildVariable } from './variableRows';
 import { currentProps, currentRef, deviations, positionMoved, targetOf, viewOf } from './objectQueries';
 import { componentRow, OFFSET_AXES, offsetKey, POSITION_AXES } from './vectorRows';
@@ -230,7 +231,8 @@ export function buildObjectSection(host: InspectorHost, holderId: string, object
 
   if (asset.type === 'container') contentSection(host, holderId, object, asset.objects.length);
 
-  if (asset.type !== 'collider' && !target) {
+  const stored = findObjectHolder(project, holderId);
+  if (stored && canAddCollider(project, stored, object)) {
     addGap(host);
     host.body.add(
       new Button('+ Add collider', {
@@ -292,12 +294,8 @@ export function refreshObjectSection(host: InspectorHost, holderId: string, obje
 }
 
 /**
- * One editable property of a placed object: writes an override, offers ↺ (back to the asset
- * or, inside a container, to the template) and ↑ (apply upwards).
- *
- * Inside a container a value has two bases – the template it follows and, one step further up,
- * the asset. Reset always goes to the nearest one, so content of a placed container offers only
- * "Reset to container"; "Apply to asset" still reaches past it, dropping the template's override.
+ * One editable property of a placed object. Reset always goes to the nearest base (the template inside
+ * a container), while "Apply to asset" reaches past it, dropping the template's override.
  */
 function propertyRow(
   host: InspectorHost,
@@ -309,14 +307,7 @@ function propertyRow(
   variable = false,
 ): FieldRow {
   const bases = () => deviations(host.state, holderId, objectId, def.key);
-  const overrideSpec: PreviewedValue<ObjectRef> = {
-    target: () => currentRef(host.state, holderId, objectId),
-    read: (ref) => ref.object.overrides[def.key],
-    current: () => currentProps(host.state, holderId, objectId)?.[def.key],
-    write: (ref, value) => ref.setOverride(def.key, value),
-    remove: (ref) => ref.setOverride(def.key, undefined),
-    commit: (value) => new SetOverrideCommand(holderId, objectId, def.key, value),
-  };
+  const overrideSpec = overrideValue(host.state, holderId, objectId, def.key);
   const fieldSlot = (field: string): ListSlot => ({
     kind: 'object',
     holderId,