Remove AgentBuilder, add file ops UI, unify code editor prompt routing

- Delete agent-builder-integration.ts, workflow-store.ts, prompts.ts (~1400줄)
- Add move_file tool + sidebar file ops (right-click menu, inline rename, drag-drop, new folder)
- Loop detection: read-only tools block at 2 repeats; planText capped at 12000 chars (fix 413)
- Route proj-gen-*/proj-plan-* to handleCodeChat; remove duplicate codeAiSystemPrompt from handleChat

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

web-ui/code.html

@@ -211,6 +211,7 @@
             <div style="display:flex;gap:4px">
               <button id="code-local-btn" onclick="openLocalFolder()" title="로컬 폴더 열기" style="background:none;border:none;cursor:pointer;color:var(--muted);font-size:14px;line-height:1;padding:0 3px">🖥️</button>
               <button onclick="codeNewFile()" title="새 파일" style="background:none;border:none;cursor:pointer;color:var(--muted);font-size:16px;line-height:1;padding:0 3px">+</button>
+              <button onclick="csbNewFolderRoot()" title="새 폴더" style="background:none;border:none;cursor:pointer;color:var(--muted);font-size:13px;line-height:1;padding:0 3px">📁</button>
               <button onclick="codeSbRefresh()" title="새로고침" style="background:none;border:none;cursor:pointer;color:var(--muted);font-size:13px;line-height:1;padding:0 3px">↺</button>
             </div>
           </div>
@@ -448,5 +449,6 @@
 </div>
 
 <script src="code.js?v=20260604s"></script>
+<div id="csb-ctx"></div>
 </body>
 </html>