feat: shared PaneHeaderActions + chat-resolve WorkspaceState fix (v2.7.7)

In-flight workspace UX work.

- Extract a shared PaneHeaderActions cluster (+/Split/Reopen/History/Close)
  used by ChatTabBar + the Workspace coder/terminal pane headers, replacing the
  divergent per-header copies; SessionLandingPage history + useWorkspacePanes
  tweaks.
- Fix coder-side correctness bug: resolveChatId read sessions.workspace_panes as
  a bare WorkspacePane[] but v2.6.5 widened it to a WorkspaceState envelope, so
  it mis-read panes and clobbered tabNumbers/nextTabNumber/closedPaneStack on
  every pane-chat write. New normalizeWorkspaceState handles either shape and
  preserves the envelope (+ regression test).
- CLAUDE.md doc-sync (coder vitest suite, deploy-by-surface, dual-remote push,
  in-flight-web-WIP staging, release-branch naming).

Web tsc + coder build + coder tests green. Builds on v2.7.6.

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

apps/web/src/components/PaneHeaderActions.tsx

@@ -0,0 +1,139 @@
+import { Code, Columns2, History, MessageSquare, Plus, RotateCcw, Terminal, X } from 'lucide-react';
+import {
+  DropdownMenu,
+  DropdownMenuContent,
+  DropdownMenuItem,
+  DropdownMenuTrigger,
+} from '@/components/ui/dropdown-menu';
+import { cn } from '@/lib/utils';
+
+// Shared pane-header action cluster: + (new) / Split / Reopen-closed-pane /
+// Session history / Close. Rendered in the chat tab bar (ChatTabBar) and the
+// desktop coder + terminal pane headers (Workspace) so all pane kinds share one
+// control set. Extracted to avoid a divergent copy per header.
+interface Props {
+  // When provided (chat panes), the "+" menu's New BooChat opens an in-pane
+  // tab. When omitted (coder/terminal panes, which can't host tabs), New BooChat
+  // splits into a new pane instead.
+  onNewTab?: () => void;
+  onSplitPane: (kind: 'chat' | 'terminal' | 'coder') => void;
+  onReopenPane?: () => void;
+  onShowHistory: () => void;
+  onRemovePane?: () => void;
+  // Highlights the History button when the pane is showing the landing page.
+  historyActive?: boolean;
+  // Positioning/spacing supplied by the parent (e.g. "ml-auto px-1").
+  className?: string;
+}
+
+const BTN =
+  '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]';
+
+export function PaneHeaderActions({
+  onNewTab,
+  onSplitPane,
+  onReopenPane,
+  onShowHistory,
+  onRemovePane,
+  historyActive,
+  className,
+}: Props) {
+  return (
+    <div className={cn('flex items-center gap-0.5 shrink-0', className)}>
+      <DropdownMenu>
+        <DropdownMenuTrigger asChild>
+          <button
+            type="button"
+            onClick={(e) => e.stopPropagation()}
+            className={BTN}
+            aria-label="New chat, terminal, or coder"
+            title="New chat / terminal / coder"
+          >
+            <Plus size={12} />
+          </button>
+        </DropdownMenuTrigger>
+        <DropdownMenuContent align="end" className="w-fit">
+          {/* Chat panes: New BooChat opens a tab in THIS pane. Coder/terminal
+              panes can't host tabs, so it splits into a new pane. */}
+          <DropdownMenuItem onSelect={onNewTab ?? (() => onSplitPane('chat'))}>
+            <MessageSquare size={14} /> New BooChat
+          </DropdownMenuItem>
+          <DropdownMenuItem onSelect={() => onSplitPane('terminal')}>
+            <Terminal size={14} /> New BooTerm
+          </DropdownMenuItem>
+          <DropdownMenuItem onSelect={() => onSplitPane('coder')}>
+            <Code size={14} /> New BooCode
+          </DropdownMenuItem>
+        </DropdownMenuContent>
+      </DropdownMenu>
+
+      <DropdownMenu>
+        <DropdownMenuTrigger asChild>
+          <button
+            type="button"
+            onClick={(e) => e.stopPropagation()}
+            className={cn(BTN, 'max-md:hidden')}
+            aria-label="Split pane"
+            title="Split pane"
+          >
+            <Columns2 size={12} />
+          </button>
+        </DropdownMenuTrigger>
+        <DropdownMenuContent align="end" className="w-fit">
+          <DropdownMenuItem onSelect={() => onSplitPane('chat')}>
+            <MessageSquare size={14} /> New BooChat
+          </DropdownMenuItem>
+          <DropdownMenuItem onSelect={() => onSplitPane('terminal')}>
+            <Terminal size={14} /> New BooTerm
+          </DropdownMenuItem>
+          <DropdownMenuItem onSelect={() => onSplitPane('coder')}>
+            <Code size={14} /> New BooCode
+          </DropdownMenuItem>
+        </DropdownMenuContent>
+      </DropdownMenu>
+
+      {onReopenPane && (
+        <button
+          type="button"
+          onClick={(e) => {
+            e.stopPropagation();
+            onReopenPane();
+          }}
+          className={cn(BTN, 'max-md:hidden')}
+          aria-label="Reopen closed pane"
+          title="Reopen closed pane"
+        >
+          <RotateCcw size={12} />
+        </button>
+      )}
+
+      <button
+        type="button"
+        onClick={(e) => {
+          e.stopPropagation();
+          onShowHistory();
+        }}
+        className={cn(BTN, 'max-md:hidden', historyActive && 'text-foreground bg-muted/50')}
+        aria-label="Session history"
+        title="Session history"
+      >
+        <History size={12} />
+      </button>
+
+      {onRemovePane && (
+        <button
+          type="button"
+          onClick={(e) => {
+            e.stopPropagation();
+            onRemovePane();
+          }}
+          className={BTN}
+          aria-label="Close pane"
+          title="Close pane"
+        >
+          <X size={12} />
+        </button>
+      )}
+    </div>
+  );
+}