fix: add explicit type annotations to extension callback parameters (#8966)

Fixes #8882

Adds explicit type annotations to all extension callback parameters
(`nodeCreated`, `beforeRegisterNodeDef`, `addCustomNodeDefs`) across 14
core extension files. While the types were already inferred from the
`ComfyExtension` interface, explicit annotations improve readability and
make the code self-documenting.

## Changes

- Annotate `node` parameter as `LGraphNode` in all `nodeCreated`
callbacks
- Annotate `nodeType` as `typeof LGraphNode` and `nodeData` as
`ComfyNodeDef` in all `beforeRegisterNodeDef` callbacks
- Annotate `defs` as `Record<string, ComfyNodeDef>` in
`addCustomNodeDefs`
- Add necessary type imports where missing

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8966-fix-add-explicit-type-annotations-to-extension-callback-parameters-30b6d73d36508125b074f509aa38145f)
by [Unito](https://www.unito.io)

src/extensions/core/groupNode.ts

@@ -1993,11 +1993,11 @@ const ext: ComfyExtension = {
       await GroupNodeConfig.registerFromWorkflow(nodes, missingNodeTypes)
     }
   },
-  addCustomNodeDefs(defs) {
+  addCustomNodeDefs(defs: Record<string, ComfyNodeDef>) {
     // Store this so we can mutate it later with group nodes
     globalDefs = defs
   },
-  nodeCreated(node) {
+  nodeCreated(node: LGraphNode) {
     if (GroupNodeHandler.isGroupNode(node)) {
       ;(node as LGraphNode & { [GROUP]: GroupNodeHandler })[GROUP] =
         new GroupNodeHandler(node)