Part of #3591 (mara: "pop ups and menus appearing should animate").
Each popover mounts fresh on open ({open ? <div> : null}, not a state
transition), so a keyframe animation on the popover element itself is
the right tool -- same shape as Shell.css's own shell-page-enter
(fade + a slight translate/scale settle), including the identical
three-rule motion-guard (base rule, prefers-reduced-motion media
query, data-motion=reduce/allow explicit overrides).
Scope: LinksMenu, SettingsMenu, UserMenu -- the three header popovers.
Not included here (posted findings on the issue instead of guessing):
the refresh-interval picker's dropdown (native <select>, whose open
popup is OS/browser chrome outside CSS reach in current browsers --
"not themed" is a platform limitation, not a bug in this component's
own styling) and the jobs graph's node animations (JobqGraph is a
@hive/shared component consumed by both swarm-ui and the per-hive
dashboard, real design/implementation work on shared infra, not a
same-shape mechanical extension of an existing pattern).
Screenshot-verified the settled (post-animation) state renders
correctly; a static screenshot cannot show an in-flight CSS animation,
so this leans on exact structural parity with the already-shipped
Shell.css pattern for the animation's own correctness.
Adds the settings surface + storage plumbing swarm-ui has been missing:
nowhere to put a client-local preference and no shared code for one to
build on. Scoped small per explicit direction ("small thing somewhere",
localStorage, theme and motion in scope for now) rather than a full
/settings route + nav entry for two toggles.
- frontend/packages/swarm-ui/src/lib/settings-storage.ts: generic
useLocalSetting<T>(key, fallback) hook - read once, write through,
stay in sync with other same-tab consumers of the same key via a
small module-level pub/sub (localStorage's own storage event only
fires cross-tab).
- frontend/packages/swarm-ui/src/lib/theme-apply.ts: tri-state
system/light/dark override, applied by setting the 16 base16 custom
properties inline on <html> (an inline style always outranks a
stylesheet rule, including a media-query-gated one) - colors.css's
own comment on its light-mode block already named this as the
intended mechanism for a future override.
- frontend/packages/swarm-ui/src/lib/motion-apply.ts: tri-state
system/reduce/allow override, applied as a data-motion attribute.
Currently inert - swarm-ui has zero CSS animations yet - included
because the marginal cost riding alongside the theme override is
near zero and it was named in the same scoping answer; the first
swarm-ui animation's own CSS is what makes this do anything.
- frontend/packages/swarm-ui/src/shell/SettingsMenu.{tsx,css}: a
header icon-button + popover holding both selects, same shape as
LinksMenu (manages its own state, not a ui/ primitive, hence no
ComponentsPage demo - same exception LinksMenu already established).
- Shell.tsx/.css: mounts the two override-application hooks once
(every route renders through one Shell), and wraps SettingsMenu +
LinksMenu in a single .shell-header-actions flex wrapper so one
margin-left: auto pushes both to the right edge together - two
adjacent auto-margins on separate elements split the space between
them instead of sitting flush.
Verified the override actually outranks the media query, not just
"looks right": seeded localStorage with each override value while
forcing the opposite OS-level prefers-color-scheme via headless
chromium, both directions render the stored override, not the forced
OS preference. Typecheck and build clean.
