Makefile fixup help (kagent-dev#1898)

Seems the AI that generated the makefile didn't utilize the help task.

This PR fixes that up so it is easier for contributors to see what make
tasks are available.

Now when running

```shell
make
```

or

```shell
make help
```

all available tasks show up as documented.

> [!Note]
> Some tasks moved location to make them render nicely under the
specific sections.

<img width="943" height="1172" alt="image"
src="https://github.com/user-attachments/assets/6f88620e-32ef-4dc1-918b-0b076fb6c1d4"
/>

---------

Signed-off-by: Marco Franssen <marco.franssen@gmail.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Author: marcofranssen