batch4: chats-in-sessions, force-send, /compact, right-rail file browser

Session 1:N Chat data model with backfill. Workspace switches to client-side
multi-tab pane management. Right-rail file browser with float-over viewer and
click-drag line selection replaces FileBrowserPane. Adds /compact streaming
summarizer (respects compact markers in context builder), force-send (cancels
in-flight, persists partial as 'cancelled', awaits cancellation completion via
deferred Promise + 5s timeout), message queue, stop generation, chat
auto-rename, session archive/unarchive with Closed Sessions section on repo
landing page. CHECK constraints on sessions.status, messages.role,
messages.status with KEEP IN SYNC comments tying to MESSAGE_ROLES /
MESSAGE_STATUSES const arrays. Deletes dead pane routes/hook and the
api.panes.* client block.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/components/AttachmentChip.tsx

@@ -0,0 +1,41 @@
+import { FileText, X } from 'lucide-react';
+import type { Attachment } from '@/lib/attachments';
+
+interface Props {
+  attachment: Attachment;
+  onRemove: (id: string) => void;
+  onPreview: (attachment: Attachment) => void;
+}
+
+export function AttachmentChip({ attachment, onRemove, onPreview }: Props) {
+  const lineCount = attachment.content.split('\n').length;
+
+  const label =
+    attachment.kind === 'lines' && attachment.range
+      ? `${attachment.filename}:${attachment.range[0]}-${attachment.range[1]}`
+      : attachment.filename;
+
+  return (
+    <div className="flex items-center gap-1.5 bg-muted/60 border border-border rounded px-2 py-0.5 text-xs font-mono">
+      <button
+        type="button"
+        onClick={() => onPreview(attachment)}
+        className="flex items-center gap-1.5 hover:bg-muted/60 transition-colors min-w-0"
+      >
+        <FileText className="size-3 shrink-0 text-muted-foreground" />
+        <span className="truncate max-w-[200px]">{label}</span>
+        <span className="text-muted-foreground whitespace-nowrap">
+          +{lineCount} lines
+        </span>
+      </button>
+      <button
+        type="button"
+        onClick={() => onRemove(attachment.id)}
+        className="ml-0.5 rounded hover:bg-muted-foreground/20 p-0.5 shrink-0"
+        aria-label="Remove attachment"
+      >
+        <X className="size-3" />
+      </button>
+    </div>
+  );
+}