feat(reader): mobile-pattern toolbar — compact row + ⋯ overflow menu under 768px

Wrapping alone isn't how polished mobile readers work. Adopt the
standard pattern (Kindle/Apple Books/Mihon) responsively:

- >= 768px: the full fixed-layout toolbar stays (wrap still absorbs
  mid-size widths) — power users keep one-click zoom/fit/spread.
- < 768px: single-line compact row — page back, back-to-location pin,
  slider, page forward, progress, and a ⋯ overflow button. No
  wrapping, no horizontal scroll.
- ⋯ opens a glass menu anchored above the bar with LABELED rows
  (Zoom −/%/+, Fit, Page position/Recenter, Magnifier, Pointer
  Smart/Pan/Text, Double page, Contents) — labels beat mystery icons
  on touch. Pointer row hides for comics; menu scrolls if tall.
- Dismissal: Esc, outside click (⋯ button exempt so it re-toggles
  cleanly), opening any drawer or TOC closes it; hides with the
  chrome. Compact slider registered in progressSliders() so all
  three stay in sync with relocate events.

web/static/input.css

@@ -991,6 +991,55 @@
     gap: 0.25rem;
   }
 
+  /* Fixed-layout toolbar responsiveness:
+     - >= 768px: full toolbar (flex-wrap absorbs mid-size widths)
+     - < 768px:  compact single line + ⋯ overflow menu (mobile-reader
+       pattern: paging/slider/progress stay, power tools get a labeled menu) */
+  .fx-compact {
+    display: none;
+  }
+  @media (max-width: 767px) {
+    .fx-tools-full {
+      display: none;
+    }
+    .fx-compact {
+      display: flex;
+    }
+  }
+  .reader-tools-popover {
+    position: absolute;
+    bottom: 100%;
+    right: 0.5rem;
+    margin-bottom: 0.5rem;
+    min-width: 16rem;
+    max-width: calc(100vw - 1.5rem);
+    max-height: min(26rem, 65vh);
+    overflow-y: auto;
+    background-color: color-mix(in srgb, var(--bg-primary) 88%, transparent);
+    -webkit-backdrop-filter: blur(18px) saturate(1.3);
+    backdrop-filter: blur(18px) saturate(1.3);
+    border: 1px solid color-mix(in srgb, var(--border) 70%, transparent);
+    border-radius: 0.75rem;
+    box-shadow: 0 -6px 28px rgba(0, 0, 0, 0.35);
+    padding: 0.25rem;
+  }
+  .reader-tools-row {
+    display: flex;
+    align-items: center;
+    justify-content: space-between;
+    gap: 1rem;
+    padding: 0.5rem 0.75rem;
+    font-size: 0.875rem;
+    border-radius: 0.5rem;
+  }
+  .reader-tools-row + .reader-tools-row {
+    border-top: 1px solid
+      color-mix(in srgb, var(--border) 45%, transparent);
+  }
+  .reader-tools-row:hover {
+    background-color: color-mix(in srgb, currentColor 6%, transparent);
+  }
+
   /* In-book search */
   .reader-search-bar {
     display: flex;