Block @pascal-app/nodes imports from framework packages

Adds a Biome noRestrictedImports rule scoped to core/, viewer/, and
editor/ packages. Framework code must reach node-specific behavior via
nodeRegistry.get(kind), never via direct import. The @pascal-app/nodes
package doesn't exist yet (lands in the next commit) so the rule is a
no-op today; codifies the boundary ahead of node bundles.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

biome.jsonc

@@ -122,6 +122,30 @@
           }
         }
       }
+    },
+    {
+      "includes": [
+        "packages/core/**/*.ts",
+        "packages/core/**/*.tsx",
+        "packages/viewer/**/*.ts",
+        "packages/viewer/**/*.tsx",
+        "packages/editor/**/*.ts",
+        "packages/editor/**/*.tsx"
+      ],
+      "linter": {
+        "rules": {
+          "style": {
+            "noRestrictedImports": {
+              "level": "error",
+              "options": {
+                "paths": {
+                  "@pascal-app/nodes": "Framework packages must not import from @pascal-app/nodes — consult nodeRegistry.get(kind) instead. See plans/editor-node-registry.md."
+                }
+              }
+            }
+          }
+        }
+      }
     }
   ]
 }