docs: correct presence tracking data based on per-client research

- Cinny upstream: ✗ → ~ (manual AFK only, auto-detection PR unmerged)
- Commet: basic → partial (inactivity monitor shipped Oct 2025, PR #475)
- Element Web/Desktop: 'no idle detection' → partial; 3-min idle timer
  shipped Nov 2023 (matrix-react-sdk PR #11824), but no tab detection,
  no offline-on-close, no user hide toggle
- FluffyChat, Element X, Nheko: basic confirmed, no change

Sources: matrix-react-sdk PR #11824, Commet PR #475, Cinny issue #2395

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

landing/index.html

@@ -1020,12 +1020,12 @@
                 <tr>
                     <td>Online presence tracking<small>idle/away auto-detection</small></td>
                     <td class="ours"><span class="yes">✓</span><small>online on start, idle after 10 min,<br>unavailable when tab hidden,<br>offline on close; hide-status toggle</small></td>
-                    <td><span class="no">✗</span></td>
-                    <td><span class="part">~</span><small>basic online/offline</small></td>
-                    <td><span class="part">~</span><small>basic online/offline</small></td>
-                    <td><span class="part">~</span><small>basic online/offline</small></td>
-                    <td><span class="part">~</span><small>basic; no idle detection on web</small></td>
-                    <td><span class="part">~</span><small>basic online/offline</small></td>
+                    <td><span class="part">~</span><small>manual AFK only; auto idle<br>detection PR open, unmerged</small></td>
+                    <td><span class="part">~</span><small>basic online/offline only</small></td>
+                    <td><span class="part">~</span><small>basic online/offline only</small></td>
+                    <td><span class="part">~</span><small>inactivity monitor shipped Oct 2025;<br>no tab/close detection confirmed</small></td>
+                    <td><span class="part">~</span><small>3-min idle timer (shipped Nov 2023);<br>no tab detection, no offline on close,<br>no user-facing hide toggle</small></td>
+                    <td><span class="part">~</span><small>basic online/offline only</small></td>
                 </tr>
                 <tr>
                     <td>Push notifications</td>