Consistent logging with name prefix in message

[pior]

Log messages now include the full composed name as a prefix, making them scannable without reading structured fields. The runnable= field is dropped.

Before:

level=INFO msg=started runnable=manager/httpserver
level=INFO msg="starting shutdown" runnable=manager reason="context cancelled"

After:

level=INFO msg="manager/httpserver: started"
level=INFO msg="manager: starting shutdown" reason="context cancelled"

Also normalized Manager() constructor to set name: "manager" directly, making runnableName() a simple one-liner like all other wrappers.