feat: v0.9.0 conversation search, plan usage meters, quiet phone at the desk

- devdesk attach --search (grep + jq over ~/.claude/projects, six files at
  a time) and --resume-convo NAME ID [fork]; devdesk-claude-run passes
  --fork-session once. Search dialog with Resume / Fork / Open.
- statusLine snapshots rate_limits and pr; footer/menu meters with a 90 %
  warning; PR chip on session rows.
- CLAUDE_CLIENT_PRESENCE_FILE per tmux session id; --presence on|off with a
  self-expiring marker; the page heartbeats it while visible.

Closes #24
Closes #25
Closes #26

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

web/index.template.html

@@ -63,6 +63,8 @@
         </div>
         <button type="button" class="dd-menu-item" id="theme-menu" role="menuitem">Light mode</button>
         <button type="button" class="dd-menu-item" id="notify-toggle" role="menuitem">Desktop notifications</button>
+        <div class="dd-menu-row dd-usage-row" id="usage-row" hidden><span>Plan usage</span><span class="dd-usage" id="usage-menu"></span></div>
+        <button type="button" class="dd-menu-item" id="history-menu" role="menuitem">Search past conversations</button>
         <button type="button" class="dd-menu-item" id="palette-menu" role="menuitem">Command palette</button>
         <button type="button" class="dd-menu-item" id="help-open" role="menuitem">Keyboard shortcuts</button>
         <button type="button" class="dd-menu-item" id="fullscreen-toggle" role="menuitem" title="In Chromium, fullscreen also captures Ctrl+W/Ctrl+T for the terminal">Fullscreen</button>
@@ -179,6 +181,7 @@
     <span class="lt-footer-hint"><span class="lt-footer-key">^⇧P</span>commands</span>
     <button type="button" class="dd-footer-help" id="footer-help">all keys</button>
   </div>
+  <div class="dd-usage dd-footer-usage" id="usage-footer" hidden></div>
   <div class="dd-keybar" id="keybar" role="toolbar" aria-label="Terminal keys" hidden>
     <button type="button" data-keys="esc">Esc</button>
     <button type="button" data-keys="tab">Tab</button>