Wave 6 chunk A: sidebar context menu (Rename/Delete) + the two-option delete dialog

- Right-click any session row: MenuShell context menu, exactly two actions
  (owner ruling): Rename and Delete… — MenuShell discipline (placement,
  focus, arrow cycling, lh:menu-open announcements), agent-section's
  outside-click/Esc contract with [data-lh-menu] carve-outs.
- Rename is INLINE in the row (owner ruling): select-all entry, Enter/blur
  commits through the existing plumbing — PUT /api/chats/:id then
  lh:chat-renamed. The open chat header now LISTENS for the event too, so
  renaming the active session from the sidebar updates the header in place
  (it only dispatched before).
- Delete opens the two-option dialog (locked design, DELETE_OPTIONS pure
  seam for render pins): "Delete the session only" (preserve-graph — the
  graph keeps every contribution) vs "Also remove its graph traces"
  (delete-nodes — shared topics survive, only-this-session topics die).
  409 turn_in_flight/jobs_running and 503 extraction_winding_down render
  the server's line verbatim with a same-mode Try-again.
- Success: the sidebar patches its snapshot instantly, the active session
  navigates home (chat unmounts — drafts die with it), and lh:graph-revision
  announces the returned revision — the graph view refetches the snapshot
  AND costs (deletion is the one writer the status poll can't see).
- ChatDeleteMode type re-exported through the core barrel (the shell's one
  needed seam from core/graph-deletion.ts).

Gates: tsc clean, 909/909, lint 0, build ok. Live-verified on :3001:
context menu open/Esc, inline rename (row + API + active header), both
delete modes on scratch sessions, simulated 409 + retry-then-succeed,
active-session navigation home, graph+costs refetch deltas on home.

components/graph-view.tsx

@@ -904,6 +904,21 @@ export function GraphView() {
 		costsHadRunning.current = pipelineRuns.length > 0;
 	}, [pipelineRuns, refreshCosts]);
 
+	/* Deletion refresh (wave 6 chunk A): the DELETE /api/chats/:id response
+	   carries the new graphRevision, and the sidebar (which owns the delete
+	   flow) announces it as lh:graph-revision. The status poll above can't
+	   see a deletion — no pipeline run ever transitions some→none for it —
+	   so this event is the one seam. Refetch the snapshot and the costs on
+	   every announcement: deletions are rare, a redundant fetch is free. */
+	useEffect(() => {
+		const onRevision = () => {
+			setRefreshTick((t) => t + 1);
+			refreshCosts();
+		};
+		window.addEventListener("lh:graph-revision", onRevision);
+		return () => window.removeEventListener("lh:graph-revision", onRevision);
+	}, [refreshCosts]);
+
 	// Layout (Option A): the positions ledger (written by the server's
 	// incremental settle after every merge) IS the layout — the renderer
 	// receives it as frozen data. The local one-shot forceAtlas2 pass runs