The Captain agents overview now defaults to the last 7 days instead of
this month, so the page opens on a more recent and actionable window.
## What changed
- Overview page, range selector, and welcome card default to `7`.
- Backend `Captain::AssistantStatsWindow::DEFAULT_RANGE` changed from
`30` to `7`, so requests without a `range` param (or with invalid
values) also resolve to the last 7 days.
## How to test
- Open Captain → Overview: the range selector should show "Last 7 days"
by default and metrics should reflect that window. Other ranges continue
to work as before.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
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