feat(reader): add sticky progress bar with chapter ticks (#4707)

Add an always-visible, opt-in progress bar with chapter tick marks in the
persistent footer, so reading progress no longer disappears like the hover
footer slider does.

- New StickyProgressBar: a 1px rounded-border capsule with a fill and
  chapter tick marks; display-only, e-ink aware, and RTL safe. Ticks render
  inside the clipped track so the rounded ends crop them and they never
  exceed the border.
- Chapter ticks come from the TOC, mapped to spine-section start fractions
  (getChapterTickFractions); the first and last ticks are trimmed so they
  do not crowd the rounded ends.
- Thread the overall size-domain reading fraction through setProgress so the
  bar fill aligns with the tick domain.
- Footer layout: when enabled the bar grows on the left and the info widgets
  group to the right with even spacing; otherwise the existing layout is
  unchanged.
- Horizontal writing mode only; vertical keeps the current footer.
- Add the showStickyProgressBar view setting, a LayoutPanel toggle, and i18n.

Closes #1616.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/readest-app/src/utils/progress.ts

@@ -1,4 +1,45 @@
 import { localizeNumber } from './number';
+import type { TOCItem } from '@/libs/document';
+
+interface ChapterTickSource {
+  getSectionFractions: () => number[];
+  resolveNavigation: (href: string) => { index?: number } | null | undefined;
+}
+
+const flattenTOCHrefs = (items: TOCItem[]): string[] =>
+  items.flatMap((item) => [
+    ...(item.href ? [item.href] : []),
+    ...(item.subitems?.length ? flattenTOCHrefs(item.subitems) : []),
+  ]);
+
+/**
+ * Reading-fraction positions (0..1) of chapter boundaries for the sticky
+ * progress bar's tick marks. Each TOC entry's href is resolved to its spine
+ * section index, then mapped to that section's start fraction (the same
+ * size-domain as the bar fill). Ticks at the book start/end are dropped and
+ * duplicates collapsed, so multiple TOC entries inside one spine file yield a
+ * single tick. The first and last remaining ticks are also dropped so they
+ * never crowd the bar's rounded ends.
+ */
+export function getChapterTickFractions(
+  view: ChapterTickSource | null | undefined,
+  toc: TOCItem[] | null | undefined,
+): number[] {
+  if (!view || !toc?.length) return [];
+  const sectionFractions = view.getSectionFractions();
+  if (!sectionFractions?.length) return [];
+  // sectionFractions = [0, ...interior boundaries..., 1]; section `i` starts at
+  // sectionFractions[i]. Keep interior starts only (1 .. length-2).
+  const lastIndex = sectionFractions.length - 1;
+  const ticks = new Set<number>();
+  for (const href of flattenTOCHrefs(toc)) {
+    const index = view.resolveNavigation(href)?.index;
+    if (typeof index === 'number' && index >= 1 && index < lastIndex) {
+      ticks.add(sectionFractions[index]!);
+    }
+  }
+  return [...ticks].sort((a, b) => a - b).slice(1, -1);
+}
 
 export function formatProgress(
   current: number | undefined,