feat: session status at a glance, file & image drop, live Ops Alerts (0.4.0)

- devdesk-state-hook (Claude UserPromptSubmit/PostToolUse/Notification/Stop/
  SessionStart/SessionEnd) records whether each session is working, waiting on
  you or idle; --list carries it. The sidebar shows it, the header shows the
  current session's state, and a pulsing "needs you" chip jumps to sessions
  waiting for input. Session refresh no longer depends on the sidebar being open.
- `devdesk attach --upload SESSION FILE BYTES` receives a file as base64
  terminal input (raw mode, exact length, size-checked, sanitised name) into
  /var/lib/devdesk/uploads/<session>/. The UI uploads dropped or pasted files and
  pastes the path into Claude, which attaches images itself.
- `devdesk alerts` / `--alerts`: firing and pending Grafana alert rules with
  severity, instances, summary and a link. The panel's "Ask Claude" types an
  investigation prompt into the current session.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/index.template.html

@@ -20,10 +20,12 @@
     </div>
     <div class="dd-session">
       <span class="lt-chip lt-chip-info" id="session-chip">—</span>
+      <span class="lt-chip dd-state-chip" id="state-chip" data-state=""></span>
       <span class="dd-pane-title" id="pane-title"></span>
     </div>
   </div>
   <div class="lt-header-right">
+    <button type="button" class="lt-chip dd-attention" id="attention-chip" title="Sessions waiting for you"></button>
     <span class="lt-ws-status" id="ws-status" data-state="connecting" role="status">
       <span class="lt-dot"></span><span id="ws-label">connecting</span>
     </span>
@@ -41,6 +43,8 @@
 <main class="dd-main">
   <section class="lt-frame dd-terminal-frame" aria-label="Terminal">
     <div id="terminal" class="dd-terminal"></div>
+    <div id="drop-overlay" class="dd-drop-overlay" hidden><span>Drop to attach to <b id="drop-session">this session</b></span></div>
+    <div id="upload-status" class="dd-upload-status" role="status" hidden></div>
     <div id="overlay" class="dd-overlay" data-tone="info" hidden>
       <div class="lt-frame dd-overlay-card" role="alertdialog" aria-labelledby="overlay-title" aria-describedby="overlay-text">
         <div class="lt-section-header" id="overlay-title">Disconnected</div>
@@ -103,21 +107,13 @@
       </div>
     </section>
 
-    <section class="lt-frame dd-widget" id="widget-alerts" data-state="stub">
-      <div class="lt-section-header">Ops Alerts <span class="lt-badge lt-badge-sm dd-soon">v2</span></div>
+    <section class="lt-frame dd-widget" id="widget-alerts" data-state="empty">
+      <div class="lt-section-header">Ops Alerts <span class="lt-badge lt-badge-sm dd-alert-count"></span></div>
       <div class="lt-section-body">
-        <ul class="dd-alert-list">
-          <li class="dd-alert">
-            <span class="lt-dot lt-dot-idle"></span>
-            <span class="dd-alert-text">No alert source connected</span>
-            <button type="button" class="lt-btn lt-btn-sm dd-ask" disabled
-                    data-ask-claude="Investigate the firing alert: ">Ask Claude</button>
-          </li>
-        </ul>
-        <p class="dd-muted dd-stub-note">Firing Grafana alerts, each with an “Ask Claude” prompt.</p>
+        <ul class="dd-alert-list"><li class="dd-empty">Loading…</li></ul>
+        <p class="dd-muted dd-stub-note dd-alerts-note"></p>
       </div>
     </section>
-
   </aside>
 </main>