Self-heal sessions whose report failed to generate at session end

A session's data (gaze/dom/mouse logs, screenshots) is written
independently of the final generate_report() call, so a one-off
failure right as tracking stops (transient, not reproducible from the
same data afterward) left otherwise-complete sessions permanently
unreachable from the landing page — listed with real stats but
un-clickable, with no way to retry. _recent_sessions_json() now
retries generate_report() for any listed session missing its report
before building the list, so it recovers automatically next time the
landing page loads. Verified against a real affected session: the
report rebuilds successfully from its existing data with no changes
to gaze/mouse capture or session recording.

browser_session.py

@@ -424,6 +424,17 @@ def _recent_sessions_json(limit=5):
     out = []
     for ts, name, full in entries[:limit]:
         report_path = os.path.join(full, "analysis_report.html")
+        if not os.path.exists(report_path):
+            # A report can fail to build once (e.g. a transient issue right
+            # as tracking stopped) even though the underlying session data
+            # is completely intact — self-heal here instead of leaving that
+            # session permanently unreachable from the landing page. Reuses
+            # the exact same generate_report() call gaze_worker() already
+            # makes at session end; no new report-building logic.
+            try:
+                generate_report(full)
+            except Exception as e:
+                print(f"[browser_session] could not (re)build report for {name}: {e}")
         report_url = None
         if os.path.exists(report_path):
             report_url = "file://" + report_path.replace(os.sep, "/")