fix: live reasoning, tool progress, in-flight session recovery (#367)

* fix: preserve live session output across chat switches

(cherry picked from commit 401e3b643d25e8dad8c06883b478b3c3073f07a5)

* fix: preserve todo state after session reload

(cherry picked from commit 7ee093ba19978af23b79148df2f2347e2f1e5bde)

* fix: preserve live assistant anchor across rerenders

* fix: stream live reasoning and tool progress

* fix: recover inflight session state after reload

* fix: add loadInflightState stub + CHANGELOG v0.50.21

- static/ui.js: add loadInflightState() function (currently returns null —
  the typeof guard in sessions.js means reload recovery works via the
  else-path attachLiveStream call; this stub satisfies the guard cleanly
  and documents the extension point for future localStorage-backed state)
- CHANGELOG.md: v0.50.21 entry; 960 tests (up from 949)

---------

Co-authored-by: Jordan SkyLF <jordan@skylinkfiber.net>
Co-authored-by: Nathan Esquenazi <nesquena@gmail.com>

static/panels.js

@@ -308,10 +308,11 @@ async function cronDelete(id) {
 function loadTodos() {
   const panel = $('todoPanel');
   if (!panel) return;
+  const sourceMessages = (S.session && Array.isArray(S.session.messages) && S.session.messages.length) ? S.session.messages : S.messages;
   // Parse the most recent todo state from message history
   let todos = [];
-  for (let i = S.messages.length - 1; i >= 0; i--) {
-    const m = S.messages[i];
+  for (let i = sourceMessages.length - 1; i >= 0; i--) {
+    const m = sourceMessages[i];
     if (m && m.role === 'tool') {
       try {
         const d = JSON.parse(typeof m.content === 'string' ? m.content : JSON.stringify(m.content));