feat: strip dcp-message-id tags from opencode output + reopen closed panes

Two independent fixes:

- opencode-server.ts: stripDcpTags() removes <dcp-message-id>…</dcp-message-id>
  tags from text deltas before they reach the frame/DB. Applied to all three
  text paths (session.next.text.delta, message.part.delta text field,
  handleUpdatedPart text type). Reasoning/tool paths untouched.
- useWorkspacePanes.ts: module-level closedPaneStack (capped at 10) captures
  pane kind + chatIds on removePane and removeTab auto-remove. reopenPane()
  pops the stack and re-attaches a new pane to the existing chat ids (chats
  survive pane close server-side). hasClosedPanes drives conditional render.
- ChatTabBar.tsx: [+] is now instant new-tab (no dropdown); split-pane
  dropdown (Columns2 icon) opens Chat/Term/Code in a new pane; reopen button
  (RotateCcw icon) appears when closed panes exist.
- Workspace.tsx: pass reopenPane + hasClosedPanes through to ChatTabBar.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/web/src/components/ChatTabBar.tsx

@@ -1,5 +1,5 @@
 import { useState } from 'react';
-import { Code, History, MessageSquare, Plus, Terminal, X } from 'lucide-react';
+import { Code, Columns2, History, MessageSquare, Plus, RotateCcw, Terminal, X } from 'lucide-react';
 import type { Chat, WorkspacePane } from '@/api/types';
 import { StatusDot } from '@/components/StatusDot';
 import {
@@ -26,7 +26,9 @@ interface Props {
   onCloseOthers: (chatId: string) => void;
   onCloseToRight: (chatId: string) => void;
   onCloseAll: () => void;
-  onAddPane: (kind: 'chat' | 'terminal' | 'coder') => void;
+  onNewTab: () => void;
+  onSplitPane: (kind: 'chat' | 'terminal' | 'coder') => void;
+  onReopenPane?: () => void;
   onShowHistory: () => void;
   onRename: (chatId: string, name: string) => Promise<void>;
   onRemovePane?: () => void;
@@ -40,7 +42,9 @@ export function ChatTabBar({
   onCloseOthers,
   onCloseToRight,
   onCloseAll,
-  onAddPane,
+  onNewTab,
+  onSplitPane,
+  onReopenPane,
   onShowHistory,
   onRename,
   onRemovePane,
@@ -131,7 +135,7 @@ export function ChatTabBar({
               </div>
             </ContextMenuTrigger>
             <ContextMenuContent>
-              <ContextMenuItem onSelect={() => onAddPane('chat')}>
+              <ContextMenuItem onSelect={onNewTab}>
                 New chat
               </ContextMenuItem>
               <ContextMenuSeparator />
@@ -170,29 +174,49 @@ export function ChatTabBar({
       )}
 
       <div className="flex items-center ml-auto gap-0.5 px-1 shrink-0">
+        <button
+          type="button"
+          onClick={onNewTab}
+          className="inline-flex items-center justify-center p-1 rounded text-muted-foreground hover:bg-muted hover:text-foreground max-md:min-h-[44px] max-md:min-w-[44px]"
+          aria-label="New tab"
+          title="New tab"
+        >
+          <Plus size={12} />
+        </button>
         <DropdownMenu>
           <DropdownMenuTrigger asChild>
             <button
               type="button"
               className="inline-flex items-center justify-center p-1 rounded text-muted-foreground hover:bg-muted hover:text-foreground max-md:min-h-[44px] max-md:min-w-[44px]"
-              aria-label="New pane"
-              title="New pane"
+              aria-label="Split pane"
+              title="Split pane"
             >
-              <Plus size={12} />
+              <Columns2 size={12} />
             </button>
           </DropdownMenuTrigger>
           <DropdownMenuContent align="end" className="w-fit">
-            <DropdownMenuItem onSelect={() => onAddPane('chat')}>
+            <DropdownMenuItem onSelect={() => onSplitPane('chat')}>
               <MessageSquare size={14} /> New BooChat
             </DropdownMenuItem>
-            <DropdownMenuItem onSelect={() => onAddPane('terminal')}>
+            <DropdownMenuItem onSelect={() => onSplitPane('terminal')}>
               <Terminal size={14} /> New BooTerm
             </DropdownMenuItem>
-            <DropdownMenuItem onSelect={() => onAddPane('coder')}>
+            <DropdownMenuItem onSelect={() => onSplitPane('coder')}>
               <Code size={14} /> New BooCode
             </DropdownMenuItem>
           </DropdownMenuContent>
         </DropdownMenu>
+        {onReopenPane && (
+          <button
+            type="button"
+            onClick={onReopenPane}
+            className="inline-flex items-center justify-center p-1 rounded text-muted-foreground hover:bg-muted hover:text-foreground max-md:min-h-[44px] max-md:min-w-[44px]"
+            aria-label="Reopen closed pane"
+            title="Reopen closed pane"
+          >
+            <RotateCcw size={12} />
+          </button>
+        )}
         <button
           type="button"
           onClick={onShowHistory}

apps/web/src/components/Workspace.tsx

@@ -65,6 +65,8 @@ export function Workspace({
     showLandingPage,
     addSplitPane,
     removePane,
+    reopenPane,
+    hasClosedPanes,
     isPaneChatPending,
     handlePaneDragStart,
     handlePaneDragOver,
@@ -207,10 +209,9 @@ export function Workspace({
                   onCloseOthers={(chatId) => closeOtherTabs(idx, chatId)}
                   onCloseToRight={(chatId) => closeTabsToRight(idx, chatId)}
                   onCloseAll={() => closeAllTabs(idx)}
-                  onAddPane={(kind) => {
-                    if (kind === 'chat') void createChat(idx);
-                    else onAddPane(kind);
-                  }}
+                  onNewTab={() => void createChat(idx)}
+                  onSplitPane={(kind) => onAddPane(kind)}
+                  onReopenPane={hasClosedPanes ? reopenPane : undefined}
                   onShowHistory={() => showLandingPage(idx)}
                   onRename={renameChat}
                   onRemovePane={panes.length > 1 ? () => removePane(idx) : undefined}