feat: right-click menus everywhere, workspace/session cost, long-term DB safety

Right-click menus: one portal shell (components/ContextMenu.tsx) for every
item with actions - sidebar/Recents/archived session rows (SessionMenu),
console tabs, pane headers, the Changes panel's files/tree/commits, the
workspace home, sessions outside a workspace (SessionRowMenu: Sessions
table, Dashboard, Activity, Workflow runs), prompt images, every Settings
list and every Claude Code/Codex config list (FileItemMenu). Buttons stay;
a delete keeps its button's confirm; the shell stops portal clicks from
reaching the card that opened it.

Status bar: Workspace $ and Session $ on the Workspace page, from
?lane= on GET /api/pricing/cost and the focused/replayed session's cost.

Database, no data dropped: synchronous=NORMAL, journal_size_limit 64 MB,
hourly PASSIVE checkpoint + PRAGMA optimize, idx_events_session_created
(replacing the redundant idx_events_session), watchdog reads
sessions.transcript_path, transcript parsed before the hook's write
transaction, GET /api/sessions/:id?events=0 for the web page (reloads only
on its own session, debounced), streamed export, transactional clear-data
and chunked cleanup, subagent import reads tool_use_ids once, runtime logs
rotated past 5 MB.

client/src/pages/Workspace.tsx

@@ -62,7 +62,7 @@ import { keepIfSame } from "../lib/keepIfSame";
 import { useLanes } from "../hooks/useLanes";
 import { LaneConsolePane } from "../components/run/LaneConsolePane";
 import { ConsoleTabs } from "../components/run/ConsoleTabs";
-import { type LayoutUpdate, PaneGrid, usePaneLayout } from "../components/run/PaneGrid";
+import { type LayoutUpdate, PaneGrid, SplitMenus, usePaneLayout } from "../components/run/PaneGrid";
 import {
   type Edge,
   type PaneLayout,
@@ -298,7 +298,7 @@ function ConsoleArea({
       onRunsChanged();
       if (!r.run_id || laneRef.current !== laneId) return;
       pending.current.set(slot, activeRuns);
-      change((l) => moveInLayout(l, slot, target, edge));
+      change((l) => moveInLayout(l.root ? l : view, slot, target, edge));
     } catch (err) {
       setSplitError(err instanceof Error ? err.message : String(err));
     }
@@ -327,8 +327,25 @@ function ConsoleArea({
           }}
           onClosed={(runId) => ended(slotOf(runId))}
           onHome={onNewSession}
-          // Per-workspace actions (mcp sync, sync-base check, readme).
-          actions={<LaneToolsMenu lane={lane} />}
+          // Per-workspace actions (mcp sync, sync-base check, readme), and
+          // while one pane is shown its split menus (a split pane has its own).
+          actions={
+            <div className="flex items-center gap-1">
+              {shown.length === 1 && shown[0] !== undefined && (
+                <SplitMenus
+                  slot={shown[0]}
+                  shown={shown}
+                  runs={tabs}
+                  label={label}
+                  // A layout never saved is the one-pane `view`: split that.
+                  onChange={(fn) => change((l) => fn(l.root ? l : view))}
+                  canStart={free !== null}
+                  onNewSplit={(target, edge) => void newSplit(target, edge)}
+                />
+              )}
+              <LaneToolsMenu lane={lane} />
+            </div>
+          }
         />
       )}
       {splitError && (