The Tavily /usage endpoint returns a nested "account" object with
plan_usage/plan_limit/search_usage/etc fields, not the flat structure
with used/limit/breakdown that was assumed. This caused all usage
values to be None.
The /status command tried to access web search config via
`loop.config.tools.web.search`, but AgentLoop has no `config` attribute.
This caused the search usage lookup to silently return None, so web
search provider usage was never displayed.
Fix: use `loop.web_config.search` which is the actual attribute
set during AgentLoop.__init__.