feat(reader): immersive chrome, slide-over drawers, tri-state PDF pointer mode

Phase 1 of the reader redesign:

- Reading surface is edge-to-edge; top/bottom bars overlay
  translucently (backdrop-blur) instead of reserving insets, killing
  the inset-coordination bug class entirely. Chrome auto-hides after
  2.5s of pointer inactivity (chrome_behavior setting finally wired:
  auto-hide / always-visible; legacy values map to auto-hide). Pointer
  activity inside page iframes keeps it awake; Esc toggles.
- TOC / Settings / Bookmarks become slide-over drawers with a scrim
  (z-50, full-height, safe-area aware), replacing the dockable-panel
  system and its window-shade headers. Only one drawer opens at a
  time; Esc or scrim click closes.
- Bottom bar is contextual: reflowable keeps nav/slider/progress/TOC;
  fixed-layout row adds Fit Page/Width select, zoom cluster,
  magnifier (now shows active state), Double Page Spread toggle, and
  a Smart | Pan | Text segmented control replacing the cryptic
  two-state icon. Smart = text-aware drag; Text = selection-only
  (manual smart-detect off); Pan = force pan. Choice persists via
  pdf_interaction_mode (new setting + foliate 29bc958 'text' mode).
- Settings drawer: Behavior (chrome, progress mode), Appearance with
  18 Kindle-style theme swatches (single source of truth from
  THEME_COLORS), Typography, Layout — each scoped by format.
- Keyboard: t/s/b open TOC/settings/bookmark, Esc closes drawers
  before toggling chrome, shortcuts skip form inputs; both slider
  rows tracked correctly (no duplicate-ID lookups).
- Topbar: Back, title, add-bookmark, bookmarks drawer, Aa settings;
  chrome follows user theme.

web/static/input.css

@@ -725,7 +725,7 @@
     border: 1px solid var(--wood-border);
   }
 
-  /* ---------- Reader ---------- */
+  /* ---------- Reader chrome & drawers ---------- */
   .reader-icon {
     display: block;
     fill: none;
@@ -735,32 +735,71 @@
     stroke-linejoin: round;
   }
 
-  .dockable-panel {
+  .drawer-scrim {
+    position: fixed;
+    inset: 0;
+    background-color: rgba(0, 0, 0, 0.45);
+    z-index: 45;
+  }
+  .reader-drawer {
+    position: fixed;
+    top: 0;
+    bottom: 0;
+    width: 340px;
+    max-width: calc(100vw - 2rem);
     background-color: var(--bg-secondary);
+    z-index: 50;
+    display: flex;
+    flex-direction: column;
+    padding-top: env(safe-area-inset-top);
+    padding-bottom: env(safe-area-inset-bottom);
+  }
+  .reader-drawer.left {
+    left: 0;
+    border-right: 1px solid var(--border);
+  }
+  .reader-drawer.right {
+    right: 0;
+    border-left: 1px solid var(--border);
+  }
+  .reader-drawer-header {
+    display: flex;
+    align-items: center;
+    justify-content: space-between;
+    padding: 0.75rem 1rem;
     border-bottom: 1px solid var(--border);
-    transition: max-height 0.2s ease-out;
+    flex-shrink: 0;
+  }
+  .reader-drawer-body {
+    flex: 1;
+    overflow-y: auto;
+    padding: 1rem;
+  }
+  .reader-seg {
+    display: inline-flex;
+    border: 1px solid var(--border);
+    border-radius: 0.5rem;
     overflow: hidden;
   }
-  .dockable-panel.panel-collapsed .panel-content {
-    display: none;
+  .reader-seg button {
+    padding: 0.25rem 0.6rem;
+    font-size: 0.75rem;
+    line-height: 1.25rem;
   }
-  .panel-header {
-    user-select: none;
+  .reader-seg button.active {
+    background-color: #2563eb;
+    color: #ffffff;
   }
-  .panel-header:hover {
-    background-color: var(--surface-hover);
+  .theme-swatch {
+    height: 2.25rem;
+    border-radius: 0.5rem;
+    border: 1px solid var(--border);
+    display: flex;
+    align-items: center;
+    justify-content: center;
   }
-  .panel-container {
-    background-color: var(--bg-secondary);
-    border-right: 1px solid var(--border);
-    width: 320px;
-    max-width: calc(100vw - 1rem);
-    max-height: 100%;
-    overflow-y: auto;
-  }
-  #right-sidebar .panel-container {
-    border-right: none;
-    border-left: 1px solid var(--border);
+  .theme-swatch:hover {
+    border-color: #3b82f6;
   }
 
   /* ---------- Series stacked covers ---------- */