Wraps every section of ServerSettingsForm (Connection Mode, Custom
Headers, Request Metadata, Timeouts, OAuth Settings) in a controlled
Mantine Accordion. The accordion is driven by new required
`expandedSections` / `onExpandedSectionsChange` props so the parent
owns expand/collapse state — consistent with the dumb-component
principle.
Adds a `variant?: "default" | "subtle"` prop to ListToggle. In subtle
mode it renders as an ActionIcon with `variant="subtle"`, `color="gray"`,
and a 16px icon so it visually matches Mantine's CloseButton in modal
headers (transparent until hover).
Adds a WithSettingsModal story on UnconnectedView that presents the
form inside a Mantine Modal with a custom three-column header: subtle
ListToggle on the left (expands/collapses all sections at once),
"Server Settings" Title centered, CloseButton on the right.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>