Apply the fixed-chrome pattern to three more list modules:
- Notifications: the inbox header (title + mark-all / clear-all) pins in
the band; only the notification list scrolls.
- Downloads: the title + subtitle + tabs pin; the tab content scrolls.
- Channel discovery: the intro + table controls pin (controlsInBand), the
table rows scroll under the sticky header (fills out the manager's
Discover tab to match Subscriptions).
Verified: headers land in the fixed band, content in the scroller. Suite
15/15, tsc + knip clean.
peter
685c7b4c0b