fix(a11y): chips, grips, the panel tab and Back to top keep the focus somewhere real

- F5: a chip's × pressed from the keyboard hands the focus to the next chip (else the previous one,
  else what follows) before it unmounts — in DismissibleChip, so all five chip rows get it
  (`focusNeighbour` in lib/useFocusKeeper).
- F4: a drag grip names what it lifts (`common.order.dragNamed`: panel groups, personal views);
  the two generic "Drag to reorder" keys are gone.
- F6: the side panel's edge tab is out of the Tab order while the card covers it, names its panel,
  and a keyboard pin moves the focus into the card.
- F7: Back to top is no Tab stop while hidden, and a keyboard press leaves the focus on the page.

frontend/src/components/ui/SidePanel.tsx

@@ -1,4 +1,4 @@
-import { useState, type ReactNode } from "react";
+import { useRef, useState, type ReactNode } from "react";
 import { useTranslation } from "react-i18next";
 import { Check, Pencil, Pin, PinOff, RotateCcw } from "lucide-react";
 import { useScrollFade } from "../../lib/useScrollFade";
@@ -64,6 +64,7 @@ export default function SidePanel({
   children: ReactNode;
 }) {
   const { t } = useTranslation();
+  const cardRef = useRef<HTMLElement>(null);
   const fade = useScrollFade();
   const peek = useHoverFocusWithin();
   const drawerMode = useMediaQuery(DRAWER_QUERY, false);
@@ -143,16 +144,29 @@ export default function SidePanel({
           hover that opened the card, and unmounting it while focused would throw keyboard focus to
           nowhere. It only goes transparent: the card's rounded corner cuts away its own pixels, and
           this square-cornered tab sits right under that arc, so it would otherwise bleed through.
-          `opacity-0` (not `invisible`/`hidden`) keeps it hoverable and focusable. */}
+          `opacity-0` (not `invisible`/`hidden`) keeps it hoverable, and a focus already on it stays.
+          But no Tab lands on it while the card covers it (E28 review F6): an invisible stop, where the
+          card's own pin says the same. A keyboard pin hands the focus into the card it opened. */}
       <Pressable
         {...(drawerMode ? {} : peek.hoverHandlers)}
-        onClick={drawerMode ? () => setDrawerOpen(true) : onToggleCollapse}
+        onClick={
+          drawerMode
+            ? () => setDrawerOpen(true)
+            : (e) => {
+                onToggleCollapse();
+                if (e.detail === 0)
+                  requestAnimationFrame(() =>
+                    cardRef.current?.querySelector<HTMLElement>("button")?.focus(),
+                  );
+              }
+        }
+        tabIndex={expanded ? -1 : undefined}
         aria-label={
           drawerMode
             ? t("sidebar.openPanel", { title })
             : pinned
-              ? t("sidebar.unpin")
-              : t("sidebar.pin")
+              ? t("sidebar.unpinNamed", { title })
+              : t("sidebar.pinNamed", { title })
         }
         aria-haspopup={drawerMode ? "dialog" : undefined}
         className={`${SURFACE.edgeTab} glass-hover absolute top-3 left-0 z-paneltab flex flex-col items-center gap-2 px-1.5 py-3 pointer-coarse:w-11 transition-opacity ${
@@ -175,6 +189,7 @@ export default function SidePanel({
 
       {expanded && (
         <aside
+          ref={cardRef}
           {...peek.hoverHandlers}
           className={`${SURFACE.panel} absolute top-3 bottom-3 left-0 z-panel w-64 flex flex-col overflow-hidden`}
         >