Add file upload functionality to the agent. Implement API endpoint for uploading files, including validation and error handling. Update web interface to support file selection and display upload status. Enhance input handling with configurable key delay for text input.

lib/agent/web/index.html

@@ -165,6 +165,8 @@
         <input id="file-path" type="text" placeholder="Directory path, e.g. C:\Users">
         <button id="file-up" type="button">Up</button>
         <button id="file-list" class="primary" type="button">List</button>
+        <button id="file-upload" type="button">Upload</button>
+        <input id="file-picker" type="file" hidden>
       </div>
       <p id="file-meta" class="meta"></p>
       <table>
@@ -208,6 +210,10 @@
       <div class="row" style="margin-top:0.75rem">
         <input id="video-text" type="text" placeholder="Type text for the focused field">
         <button id="video-send" class="primary" type="button">Send</button>
+        <label>Key delay
+          <input id="video-key-delay" type="range" min="0" max="200" value="25" style="width:8rem; vertical-align:middle">
+          <span id="video-key-delay-val">25</span> ms
+        </label>
       </div>
     </section>
     <section id="exec" class="panel">