feat: persist active main tab to localStorage

On tab click, store the tab name under 'activeMainTab' in localStorage.
On DOMContentLoaded, restore the previously active tab instead of
always defaulting to 'queue'.

Exported getActiveMainTab/setActiveMainTab for testability, following
the same pattern as getTaskFilterTab/setTaskFilterTab.

Tests: web/test/tab-persistence.test.mjs (6 tests, all green).

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

1 files changed, 11 insertions, 1 deletions

diff --git a/web/app.js b/web/app.js
index 6070d2c..9a5a460 100644
--- a/web/app.js
+++ b/web/app.js
@@ -407,6 +407,14 @@ export function setTaskFilterTab(tab) {
   localStorage.setItem('taskFilterTab', tab);
 }
 
+export function getActiveMainTab() {
+  return localStorage.getItem('activeMainTab') ?? 'queue';
+}
+
+export function setActiveMainTab(tab) {
+  localStorage.setItem('activeMainTab', tab);
+}
+
 // ── Tab badge counts ───────────────────────────────────────────────────────────
 
 /**
@@ -2721,6 +2729,8 @@ async function renderDropsPanel() {
 // ── Tab switching ─────────────────────────────────────────────────────────────
 
 function switchTab(name) {
+  setActiveMainTab(name);
+
   // Update tab button active state
   document.querySelectorAll('.tab').forEach(btn => {
     btn.classList.toggle('active', btn.dataset.tab === name);
@@ -2746,7 +2756,7 @@ if (typeof document !== 'undefined') document.addEventListener('DOMContentLoaded
     handleStartNextTask(this);
   });
 
-  switchTab('queue');
+  switchTab(getActiveMainTab());
   startPolling();
   connectWebSocket();