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/FileMentionPopover.tsx

@@ -0,0 +1,145 @@
+import { useEffect, useMemo, useRef, useState } from 'react';
+import { cn } from '@/lib/utils';
+
+interface Props {
+  query: string;
+  files: string[];
+  anchorRect: { top: number; left: number };
+  onSelect: (path: string) => void;
+  onClose: () => void;
+}
+
+function filterAndRank(files: string[], query: string): string[] {
+  const q = query.toLowerCase();
+  if (!q) {
+    return files.slice(0, 20);
+  }
+
+  const filenameMatches: string[] = [];
+  const pathOnlyMatches: string[] = [];
+
+  for (const file of files) {
+    const lower = file.toLowerCase();
+    if (!lower.includes(q)) continue;
+    const basename = file.split('/').pop() ?? file;
+    if (basename.toLowerCase().includes(q)) {
+      filenameMatches.push(file);
+    } else {
+      pathOnlyMatches.push(file);
+    }
+  }
+
+  filenameMatches.sort((a, b) => a.localeCompare(b));
+  pathOnlyMatches.sort((a, b) => a.localeCompare(b));
+
+  return [...filenameMatches, ...pathOnlyMatches].slice(0, 20);
+}
+
+export function FileMentionPopover({
+  query,
+  files,
+  anchorRect,
+  onSelect,
+  onClose,
+}: Props) {
+  const [highlightIndex, setHighlightIndex] = useState(0);
+  const popoverRef = useRef<HTMLDivElement>(null);
+  const filtered = useMemo(() => filterAndRank(files, query), [files, query]);
+
+  // Reset highlight when query changes
+  useEffect(() => {
+    setHighlightIndex(0);
+  }, [query]);
+
+  // Keyboard navigation
+  useEffect(() => {
+    function handleKeyDown(e: KeyboardEvent) {
+      if (e.key === 'ArrowDown') {
+        e.preventDefault();
+        setHighlightIndex(prev =>
+          prev < filtered.length - 1 ? prev + 1 : 0
+        );
+      } else if (e.key === 'ArrowUp') {
+        e.preventDefault();
+        setHighlightIndex(prev =>
+          prev > 0 ? prev - 1 : filtered.length - 1
+        );
+      } else if (e.key === 'Enter') {
+        e.preventDefault();
+        if (filtered.length > 0) {
+          onSelect(filtered[highlightIndex] ?? filtered[0]!);
+        }
+      } else if (e.key === 'Escape') {
+        e.preventDefault();
+        onClose();
+      }
+    }
+
+    document.addEventListener('keydown', handleKeyDown);
+    return () => document.removeEventListener('keydown', handleKeyDown);
+  }, [filtered, highlightIndex, onSelect, onClose]);
+
+  // Click outside to close
+  useEffect(() => {
+    function handleMouseDown(e: MouseEvent) {
+      if (
+        popoverRef.current &&
+        !popoverRef.current.contains(e.target as Node)
+      ) {
+        onClose();
+      }
+    }
+
+    document.addEventListener('mousedown', handleMouseDown);
+    return () => document.removeEventListener('mousedown', handleMouseDown);
+  }, [onClose]);
+
+  // Scroll highlighted item into view
+  useEffect(() => {
+    const el = popoverRef.current?.querySelector('[data-highlighted="true"]');
+    if (el) {
+      el.scrollIntoView({ block: 'nearest' });
+    }
+  }, [highlightIndex]);
+
+  if (filtered.length === 0) {
+    return (
+      <div
+        ref={popoverRef}
+        className="fixed z-50 bg-popover border border-border rounded-md shadow min-w-[260px] p-2"
+        style={{ top: anchorRect.top, left: anchorRect.left }}
+      >
+        <div className="text-xs text-muted-foreground px-2 py-1">
+          No matching files
+        </div>
+      </div>
+    );
+  }
+
+  return (
+    <div
+      ref={popoverRef}
+      className="fixed z-50 bg-popover border border-border rounded-md shadow min-w-[260px] max-h-[240px] overflow-y-auto"
+      style={{ top: anchorRect.top, left: anchorRect.left }}
+    >
+      {filtered.map((file, i) => (
+        <button
+          key={file}
+          type="button"
+          data-highlighted={i === highlightIndex}
+          className={cn(
+            'w-full text-left text-xs font-mono px-2 py-1.5 cursor-pointer',
+            i === highlightIndex && 'bg-muted'
+          )}
+          onMouseEnter={() => setHighlightIndex(i)}
+          onMouseDown={(e) => {
+            e.preventDefault();
+            onSelect(file);
+          }}
+        >
+          {file}
+        </button>
+      ))}
+    </div>
+  );
+}