feat: v0.12.0 Settings window, per-session Remote Control, delete conversations

- Settings (⋯ → Settings…, palette): theme, terminal text size, interface
  size, notifications, Remote Control & privacy. The ⋯ menu shrinks.
- Remote Control per session: registry choice > Settings default >
  DEVDESK_REMOTE_CONTROL. Switching an idle session restarts its Claude
  on the same conversation; busy sessions change at the next start.
  rc_active comes from the running process; RC tag on sessions.
- --delete-convo: remove a conversation's local transcript and subagent
  files; refused while in use. Delete… in Search past conversations.
Closes #61

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WHRLCCdXYm41Qx5kNhehaP

web/index.template.html

@@ -53,16 +53,7 @@
     <div class="dd-more">
       <button type="button" class="lt-btn lt-btn-ghost lt-btn-sm dd-more-toggle" id="more-toggle" aria-haspopup="menu" aria-expanded="false" title="Settings" aria-label="Settings">⋯</button>
       <div class="dd-menu dd-more-menu" id="more-menu" role="menu" hidden>
-        <div class="dd-menu-row">
-          <span>Text size</span>
-          <span class="dd-menu-inline">
-            <button type="button" class="dd-icon-btn" id="font-down" aria-label="Smaller text">A−</button>
-            <span id="font-size">14</span>
-            <button type="button" class="dd-icon-btn" id="font-up" aria-label="Larger text">A+</button>
-          </span>
-        </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>
+        <button type="button" class="dd-menu-item" id="settings-menu" role="menuitem">Settings…</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>