Persist branching and timeline expanded toggles across reload

Store branchingEnabled and timelineExpanded in localStorage. Restore
on init with matching UI state (button class, expand arrow, bar class).
Also persist the forced collapse when branching is disabled.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

js/snapshot_manager.js

@@ -44,8 +44,8 @@ let svgClipCounter = 0;        // unique prefix for SVG clipPath IDs
 let sidebarTooltipEl = null;   // tooltip element for sidebar hover previews
 const lastCapturedIdMap = new Map(); // workflowKey -> id of most recent capture (for parentId chaining)
 const activeBranchSelections = new Map(); // forkPointId -> selected child index
-let branchingEnabled = true;
-let timelineExpanded = false;
+let branchingEnabled = localStorage.getItem("snapshotManager_branchingEnabled") !== "false";
+let timelineExpanded = localStorage.getItem("snapshotManager_timelineExpanded") === "true";
 const sessionWorkflows = new Map(); // workflowKey -> { firstSeen, lastSeen }
 
 // ─── Server API Layer ───────────────────────────────────────────────
@@ -2807,11 +2807,12 @@ async function buildSidebar(el) {
     });
 
     const branchToggleBtn = document.createElement("button");
-    branchToggleBtn.className = "snap-filter-auto-btn active";
+    branchToggleBtn.className = "snap-filter-auto-btn" + (branchingEnabled ? " active" : "");
     branchToggleBtn.textContent = "Branch";
     branchToggleBtn.title = "Toggle snapshot branching";
     branchToggleBtn.addEventListener("click", async () => {
         branchingEnabled = !branchingEnabled;
+        localStorage.setItem("snapshotManager_branchingEnabled", branchingEnabled);
         branchToggleBtn.classList.toggle("active", branchingEnabled);
         activeBranchSelections.clear();
         if (sidebarRefresh) await sidebarRefresh().catch(() => {});
@@ -3610,10 +3611,11 @@ function buildTimeline() {
 
     const expandBtn = document.createElement("button");
     expandBtn.className = "snap-timeline-snap-btn snap-timeline-expand-btn";
-    expandBtn.textContent = "\u25B4";
-    expandBtn.title = "Expand timeline to show all branches";
+    expandBtn.textContent = timelineExpanded ? "\u25BE" : "\u25B4";
+    expandBtn.title = timelineExpanded ? "Collapse timeline" : "Expand timeline to show all branches";
     expandBtn.addEventListener("click", () => {
         timelineExpanded = !timelineExpanded;
+        localStorage.setItem("snapshotManager_timelineExpanded", timelineExpanded);
         expandBtn.textContent = timelineExpanded ? "\u25BE" : "\u25B4";
         expandBtn.title = timelineExpanded ? "Collapse timeline" : "Expand timeline to show all branches";
         bar.classList.toggle("snap-timeline-expanded", timelineExpanded);
@@ -3624,6 +3626,7 @@ function buildTimeline() {
     bar.appendChild(expandBtn);
     bar.appendChild(snapBtn);
 
+    if (timelineExpanded) bar.classList.add("snap-timeline-expanded");
     canvasParent.appendChild(bar);
     timelineEl = bar;
 
@@ -3666,6 +3669,7 @@ function buildTimeline() {
         expandBtn.style.display = branchingEnabled ? "" : "none";
         if (!branchingEnabled && timelineExpanded) {
             timelineExpanded = false;
+            localStorage.setItem("snapshotManager_timelineExpanded", "false");
             bar.classList.remove("snap-timeline-expanded");
             expandBtn.textContent = "\u25B4";
         }