feat: session rename + graph chrome polish (popovers dismiss, no-shift no-match, coverage reseat)

Rename (owner ask): clicking the header title opens edit mode with the
whole title selected — typing replaces, arrows move inside. Enter or a
click away commits (PUT /api/chats/:id); Escape and an empty commit
discard. renameChat joins the ChatStore port; like saveSettings it is
NOT conversation activity — updatedAt stays put so sidebar order never
churns on a rename. The sidebar patch is instant: the header dispatches
lh:chat-renamed and SessionsSidebar folds it into its snapshot (the 2.5s
poll is only a backstop). Sidebar right-click rename is DELIBERATELY
deferred: it needs a real context-menu system, which gets its own pass
later (owner decision, 2026-09-17).

Graph chrome:
- The extraction-coverage button moves between search and import; the
  gear keeps the far-right corner. Coverage still renders on an EMPTY
  graph (that is exactly when it matters).
- The no-match search note no longer shifts its siblings: the chrome
  row is items-start (every button is 44px tall, so top alignment pins
  the row while the search container grows downward).
- Popovers dismiss properly: pointerdown anywhere outside the control's
  root (button + panel) closes it, and so does Escape. Two panels can
  never be open at once — the sibling chrome buttons are outside the open
  root, so pointerdown closes the first before the click opens the
  second. New shared hook components/popover-dismiss.ts, wired into
  both the settings gear and the coverage control.

Gates: typecheck, eslint, 498/498 (+2 rename store tests), build.
Live-verified: select-all/focus/Enter/Escape/empty/blur round-trip,
updatedAt untouched, sidebar instant patch; chrome order + frozen
positions under a no-match query; popover close via canvas, search
input, Esc, mutual exclusion, toggle intact.

components/graph-coverage.tsx

@@ -1,6 +1,7 @@
 "use client";
 
-import { useCallback, useEffect, useState } from "react";
+import { useCallback, useEffect, useRef, useState } from "react";
+import { usePopoverDismiss } from "@/components/popover-dismiss";
 import { ListChecksIcon, Loader2Icon } from "lucide-react";
 import { formatTokens } from "@/components/usage-format";
 
@@ -34,6 +35,10 @@ interface CoverageChat {
 
 export function GraphCoverageControl({ refreshKey = 0 }: { refreshKey?: number }) {
 	const [open, setOpen] = useState(false);
+	// Click anywhere outside (or Escape) closes the panel (2026-09-17) —
+	// the root wraps button + panel, so the toggle itself keeps working.
+	const rootRef = useRef<HTMLDivElement>(null);
+	usePopoverDismiss(rootRef, open, () => setOpen(false));
 	const [chats, setChats] = useState<CoverageChat[]>([]);
 	const [loaded, setLoaded] = useState(false);
 	const [extracting, setExtracting] = useState<string[]>([]); // click-pending ids (optimistic until the poll says running)
@@ -83,7 +88,7 @@ export function GraphCoverageControl({ refreshKey = 0 }: { refreshKey?: number }
 
 	const pending = (chat: CoverageChat) => chat.running || extracting.includes(chat.chatId);
 	return (
-		<div className="relative">
+		<div ref={rootRef} className="relative">
 			<button
 				type="button"
 				title="Extraction coverage — what the knowledge graph has covered"