feat(audit): Batch 17 — screen scroll contract + History virtualization (L161, L104)

L161: <main> is now a non-scrolling flex slot; each screen owns its scroll
via shared shells in ui/Screen.tsx — 'page' (Library/Settings/empty History
scroll the shell) and 'fill' (Downloads/Terminal/History scroll their own
list/log, shell scrolls only as short-window fallback). height:100%
couplings replaced with flexGrow+minHeight:0; list regions floored at
160px so they can't collapse on short windows.

L104: HistoryView renders through VirtualList; Ctrl+A re-homed onto a
wrapper around the scroller, per-row Delete unchanged on rows.

Verified with an Electron probe against the vite preview at 1100x720 and
800x520 (probe metrics + screenshots): one active scroller per screen,
main/body never scroll, floors hold. Adds .claude/launch.json for the
preview server.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CODE-AUDIT.md

@@ -992,13 +992,13 @@ token system + shared primitives (UI/SIMP — high value, larger effort) · i18n
   `<Spinner size="tiny">` (Fetch/Index/Check-for-new/yt-dlp update/app-update/PO-mint/version-check); the only
   remaining `<Spinner>`s are standalone status-row indicators (the "Fetching…"/"Waiting to start…"/indexing
   rows), not a button + adjacent spinner. No separate-adjacent-spinner pattern survives.*
-- [ ] **L104 — History isn't virtualized.** It renders all filtered rows, while Downloads and Library use `VirtualList`.
-  *Deferred (bounded; needs the L161 layout rework + live verification): History is capped at 500 rows (L141),
-  so the un-virtualized render is bounded — not a real perf problem. Virtualizing it requires giving the list a
-  fixed-height internal scroll container (the same `height:100%`/`overflow` rework L161 flags as needing
-  live verification at multiple window sizes) *and* re-homing its container-level Ctrl+A and per-row Delete
-  keyboard handling onto the virtualized scroller. That's a layout+interaction change best done watched, so it
-  rides with L161 rather than shipping unattended for a list that's already capped.*
+- [x] **L104 — History isn't virtualized.** It renders all filtered rows, while Downloads and Library use `VirtualList`.
+  *Fixed (Batch 17, with L161): HistoryView renders through the shared `VirtualList` inside the new `fill`
+  screen shell — the list owns an internal scroll region (flex + 160px floor, DownloadsView's contract). The
+  container-level Ctrl+A moved onto a wrapper around the virtualized scroller (key events bubble up from the
+  rows), and per-row Delete stays on each row so it works wherever the row mounts. Verified live in an
+  Electron probe against the vite preview at 1100×720 and 800×520: rows render via `[data-index]` virtual
+  wrappers, the list scrolls internally, and `<main>`/body never scroll (probe metrics + screenshots).*
 - [x] **L105 — `MediaKind` declared twice.** In both [ipc.ts](src/shared/ipc.ts) and
   [store/downloads.ts](src/renderer/src/store/downloads.ts); components import it from both. Single source it.
   *Fixed: the store now imports `MediaKind` from `@shared/ipc` and re-exports it, so the duplicate local
@@ -1301,12 +1301,18 @@ token system + shared primitives (UI/SIMP — high value, larger effort) · i18n
   8px) instead of style classes (extends L5). *Fixed: the margin literals now draw from `SPACE`
   (`hairline`/`xtight`/`tight`) — same values, one source. (The broader inline-`style` vs makeStyles split is
   still L5.)*
-- [ ] **L161 — `height: 100%` screens inside a padded scroll container.** Downloads/Terminal set
+- [x] **L161 — `height: 100%` screens inside a padded scroll container.** Downloads/Terminal set
   `height: 100%` while App's `<main>` is `overflowY: auto` + 24/28px padding — a fragile coupling that can
-  double-scroll or misalign the virtualized list's viewport. *Deferred (layout, needs live verification): it
-  works today (the virtualized queue scrolls correctly), and reworking the `<main>` scroll/height contract is
-  a layout change best validated with the app open at several window sizes — a watched pass, not an unattended
-  edit.*
+  double-scroll or misalign the virtualized list's viewport. *Fixed (Batch 17): `<main>` no longer scrolls or
+  pads — it's a plain flex slot, and each screen owns its scrolling through two shared shells in
+  [ui/Screen.tsx](src/renderer/src/components/ui/Screen.tsx): `page` (document screens — Library, Settings,
+  empty History: the shell scrolls) and `fill` (internally-scrolling screens — Downloads, Terminal, History:
+  the screen's list/log is the scroller, with the shell scrolling only as the short-window fallback). The
+  `height:100%` couplings are gone (`flexGrow:1; minHeight:0` inside the shell instead). The rework surfaced a
+  real pre-existing edge: on a very short window the flexed list collapsed to 0px — now floored at 160px with
+  the shell absorbing the overflow. Verified with an Electron probe at 1100×720 and 800×520 per screen:
+  exactly one active scroller per screen in the normal case, `<main>`/body never scroll, floors hold
+  (probe metrics + screenshots).*
 - [ ] **L162 — Per-thumbnail store subscription.** Every `MediaThumb` calls `useResolvedDark()` (two store
   subscriptions) instead of receiving a resolved theme prop — N subscriptions per list. *Deferred — same as
   PERF6: virtualization/the 500-cap bounds the mounted count, and a prop conflicts with PERF5's hoisted