feat: Add search_aliases field to node schema

Adds `search_aliases` field to improve node discoverability. Users can define alternative search terms for nodes (e.g., "text concat" → StringConcatenate).

Changes:
- Add `search_aliases: list[str]` to V3 Schema
- Add `SEARCH_ALIASES` support for V1 nodes
- Include field in `/object_info` response
- Add aliases to high-priority core nodes

V1 usage:
```python
class MyNode:
    SEARCH_ALIASES = ["alt name", "synonym"]
```

V3 usage:
```python
io.Schema(
    node_id="MyNode",
    search_aliases=["alt name", "synonym"],
    ...
)
```

## Related PRs
- Frontend: Comfy-Org/ComfyUI_frontend#XXXX (draft - merge after this)
- Docs: Comfy-Org/docs#XXXX (draft - merge after stable)

comfy_extras/nodes_string.py

@@ -11,6 +11,7 @@ class StringConcatenate(io.ComfyNode):
             node_id="StringConcatenate",
             display_name="Concatenate",
             category="utils/string",
+            search_aliases=["text concat", "join text", "merge text", "combine strings", "concat", "concatenate", "append text", "combine text", "string"],
             inputs=[
                 io.String.Input("string_a", multiline=True),
                 io.String.Input("string_b", multiline=True),