Precedent attachment UI in the compose screen

Surface the new POST/GET/DELETE /api/cases/{n}/precedents endpoints
in the compose screen as two insertion points:

1. A new case-level card "פסיקה כללית לדיון" at the top of the
   main column, for precedents that support the discussion intro
   rather than a specific threshold_claim / issue.
2. An inline "פסיקה תומכת" section inside each SubsectionCard,
   below the ChairEditor.

Both insertion points render a `<PrecedentsSection>` which shows a
list of `<PrecedentCard>` (citation + blockquote + optional chair
note + 📄 chip if a PDF was archived) followed by a `<PrecedentAttacher>`
popover trigger.

The Attacher is a Popover with cross-case typeahead: typing 2+
characters into the citation field hits /api/precedents/search and
shows distinct library matches; picking one prefills quote + chair
note but leaves them editable so customizing the quote for this
case doesn't mutate the library. An optional PDF/DOCX/DOC file can
be attached — it uploads first via POST .../upload-pdf and the
returned document_id is passed into the precedent create call.

The parent compose page issues a single useCasePrecedents query
and partitions the result by section_id into a Map so each
SubsectionCard renders its own slice without re-fetching.

shadcn Popover installed as a new primitive. sonner toasts wired
for success/error in both attach and delete flows.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

web-ui/src/components/compose/precedent-card.tsx

@@ -0,0 +1,77 @@
+"use client";
+
+import { Trash2, FileText } from "lucide-react";
+import { toast } from "sonner";
+import { Button } from "@/components/ui/button";
+import { useDeletePrecedent, type CasePrecedent } from "@/lib/api/precedents";
+
+/*
+ * Read-only display of a single attached precedent. Layout is:
+ *
+ *   ┌───────────────────────────────────────────┐
+ *   │ citation (gold semibold)        [🗑]    │
+ *   │ ┌──┐                                     │
+ *   │ │╎ │  "quote text…"                      │
+ *   │ └──┘                                     │
+ *   │ chair_note (muted)                       │
+ *   │ 📄 קובץ מצורף                            │
+ *   └───────────────────────────────────────────┘
+ */
+
+export function PrecedentCard({
+  caseNumber,
+  precedent,
+}: {
+  caseNumber: string;
+  precedent: CasePrecedent;
+}) {
+  const del = useDeletePrecedent(caseNumber);
+
+  const onDelete = async () => {
+    if (!window.confirm("להסיר פסיקה זו מהתיק?")) return;
+    try {
+      await del.mutateAsync(precedent.id);
+      toast.success("הפסיקה הוסרה");
+    } catch (e) {
+      toast.error(e instanceof Error ? e.message : "שגיאה בהסרה");
+    }
+  };
+
+  return (
+    <article className="rounded-lg border border-rule bg-parchment/40 px-4 py-3 space-y-2">
+      <div className="flex items-start gap-3">
+        <p className="flex-1 text-[0.82rem] text-gold-deep font-semibold leading-snug">
+          {precedent.citation}
+        </p>
+        <Button
+          type="button"
+          variant="ghost"
+          size="sm"
+          onClick={onDelete}
+          disabled={del.isPending}
+          aria-label="הסר פסיקה זו"
+          className="text-danger hover:text-danger hover:bg-danger-bg shrink-0 -mt-1 -me-2"
+        >
+          <Trash2 className="w-4 h-4" aria-hidden="true" />
+        </Button>
+      </div>
+
+      <blockquote className="border-e-2 border-gold pe-3 text-sm text-ink leading-relaxed whitespace-pre-line">
+        {precedent.quote}
+      </blockquote>
+
+      {precedent.chair_note && (
+        <p className="text-[0.78rem] text-ink-muted italic">
+          {precedent.chair_note}
+        </p>
+      )}
+
+      {precedent.pdf_document_id && (
+        <div className="flex items-center gap-1.5 text-[0.72rem] text-ink-muted">
+          <FileText className="w-3 h-3" aria-hidden="true" />
+          <span>קובץ מצורף</span>
+        </div>
+      )}
+    </article>
+  );
+}