UnboundLocalError when using defer_loading with no base tools

## Bug Description

When using `defer_loading=True` for **all** servers (no base tools loaded directly), the Gradio UI crashes with an `UnboundLocalError` because `make_click_handler` is defined inside a `for` loop that never executes when there are no base tools.

## Steps to Reproduce

```python
from toolsets import Server, Toolset

toolset = Toolset("Test")

# Add server with deferred loading (all tools deferred, no base tools)
toolset.add(
Server("https://example.com/mcp"),
defer_loading=True
)

# This crashes
toolset.launch(mcp_server=True)
```

## Error

```
File "...\toolsets\gradio_ui.py", line 111, in launch_gradio_ui
make_click_handler(search_tool_data["inputSchema"]),
^^^^^^^^^^^^^^^^^^
UnboundLocalError: cannot access local variable 'make_click_handler' where it is not associated with a value
```

## Root Cause

In `gradio_ui.py`, the `make_click_handler` function is defined inside the `for` loop at line 81:

```python
for tool_name, tool_data in toolset._tool_data.items():
# ...
def make_click_handler(schema):
return lambda: schema
# ...
```

When all tools are deferred, `toolset._tool_data` is empty, so the loop never executes and `make_click_handler` is never defined. Later, at line 111, the code tries to use `make_click_handler` for the deferred tools UI, causing the error.

## Suggested Fix

Move the `make_click_handler` definition **before** the `for` loop:

```python
# Define before the loop
def make_click_handler(schema):
return lambda: schema

for tool_name, tool_data in toolset._tool_data.items():
h = gr.HTML(...)
h.click(make_click_handler(tool_data["inputSchema"]), outputs=j)
```

## Environment

- toolsets version: 0.1.9
- Python: 3.14
- OS: Windows 11

## Workaround

Users can manually patch `gradio_ui.py` by moving the function definition outside the loop.