v1.9: settings pane + per-project defaults + bulk archive + themes lift

Adds a singleton, ephemeral 'settings' pane kind to the workspace.
Opened via a new bottom-pinned button in ProjectSidebar (emits an
open_settings_pane event when a session is mounted; navigates to
/settings otherwise). Pane has three sections — Session, Project,
Theme — and a maximize toggle that hides sibling pane columns via
display:none on desktop only. Settings panes don't count toward
MAX_PANES and are filtered out of the localStorage persistence layer
so reload always restores a clean workspace.

Schema (additive):
- projects.default_system_prompt TEXT NOT NULL DEFAULT ''
- projects.default_web_search_enabled BOOLEAN NOT NULL DEFAULT false
- sessions.web_search_enabled BOOLEAN  (nullable; null = inherit)

Inference resolves user_prompt = session.system_prompt.trim() ||
project.default_system_prompt.trim() — empty/whitespace at either
layer means "no override". Keeps the columns NOT NULL and matches
the existing inherit semantics.

Server routes:
- GET /api/projects/:id (new; settings pane refetches on
  project_updated)
- PATCH /api/projects/:id accepts default_system_prompt,
  default_web_search_enabled
- PATCH /api/sessions/:id accepts web_search_enabled (tri-state)
- POST /api/projects/:id/sessions/archive-all + GET
  /api/projects/:id/sessions/open-count
- POST /api/sessions/:id/chats/archive-all + GET
  /api/sessions/:id/chats/open-count
- PATCH /api/sessions/:id now broadcasts session_updated on every
  successful PATCH (was rename-only). Lets SettingsPane open in
  another tab pick up edits without a refetch.

Bulk-archive publishes one session_archived / chat_archived frame
per affected id so useSidebar's existing reducer cases handle them
incrementally — no new frame type, no payload widening.

ModelPicker refactored: shared ModelList inside a responsive shell.
Desktop = labeled trigger + DropdownMenu, mobile = icon-only Cpu
button + BottomSheet. Header in Session.tsx drops the pill wrap on
mobile since the new trigger is the visual.

ChatInput gains an icon-only '+' DropdownMenu next to AgentPicker
when sessionId + webSearchEnabled props are provided. One item for
now — Web search — with a checkmark reflecting the stored value
(true), not the effective one. Click PATCHes the override; to
restore inherit-from-project the user opens SettingsPane.

ThemePicker lifted out of pages/Settings.tsx into a reusable
component. The standalone /settings route is now a thin wrapper
that mounts <ThemePicker /> with a Back button on top
(navigate(-1) with fallback to '/'); the SettingsPane Theme tab
renders the same picker bare.

Project section delete-flow removed (button + confirm dialog +
handler). Replaced with "Archive all sessions" using the same
two-step count → confirm → fire pattern as "Archive all chats" in
the Session section. api.projects.remove() stays in the client
because useProjects.ts still uses it.

Hand-rolled Switch primitive in SettingsPane (no shadcn switch in
the project; spec said no new deps). Section nav is plain buttons
(no shadcn Tabs).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/components/ChatInput.tsx

@@ -1,8 +1,14 @@
 import { useCallback, useEffect, useRef, useState, type DragEvent, type KeyboardEvent } from 'react';
-import { Send } from 'lucide-react';
+import { Check, Plus, Send } from 'lucide-react';
 import { toast } from 'sonner';
 import { Textarea } from '@/components/ui/textarea';
 import { Button } from '@/components/ui/button';
+import {
+  DropdownMenu,
+  DropdownMenuContent,
+  DropdownMenuItem,
+  DropdownMenuTrigger,
+} from '@/components/ui/dropdown-menu';
 import {
   flattenToMessage,
   inferLanguage,
@@ -29,11 +35,18 @@ interface Props {
   // When omitted, the toolbar row is hidden entirely.
   agentId?: string | null;
   onAgentChange?: (agentId: string | null) => void | Promise<void>;
+  // v1.9: when sessionId + webSearchEnabled are both provided, the + menu
+  // renders next to the AgentPicker with a single "Web search" toggle item.
+  // The check reflects the *stored* session value (not the effective one):
+  // null counts as unchecked. Clicking PATCHes session.web_search_enabled
+  // with the inverted boolean (null → true, true → false, false → true).
+  sessionId?: string;
+  webSearchEnabled?: boolean | null;
   onSend: (content: string) => void | Promise<void>;
   onForceSend?: (content: string) => void | Promise<void>;
 }
 
-export function ChatInput({ disabled, projectId, agentId, onAgentChange, onSend, onForceSend }: Props) {
+export function ChatInput({ disabled, projectId, agentId, onAgentChange, sessionId, webSearchEnabled, onSend, onForceSend }: Props) {
   const { isMobile } = useViewport();
   const [value, setValue] = useState('');
   const [busy, setBusy] = useState(false);
@@ -425,16 +438,51 @@ export function ChatInput({ disabled, projectId, agentId, onAgentChange, onSend,
           ))}
         </div>
       )}
-      {/* Batch 9 toolbar — agent picker. Sits above the input row so it
-          doesn't compete with the send button for vertical alignment.
-          When Batch 7 lands, ModelPicker and the + button join this row. */}
-      {onAgentChange && (
+      {/* Batch 9 toolbar — agent picker. v1.9 adds the icon-only + menu next
+          to it for quick toggles (currently: Web search). When omitted at the
+          callsite the row stays collapsed so nothing else has to change. */}
+      {(onAgentChange || sessionId) && (
         <div className="px-4 pt-2 flex items-center gap-1.5">
-          <AgentPicker
-            projectId={projectId}
-            value={agentId ?? null}
-            onChange={onAgentChange}
-          />
+          {onAgentChange && (
+            <AgentPicker
+              projectId={projectId}
+              value={agentId ?? null}
+              onChange={onAgentChange}
+            />
+          )}
+          {sessionId && (
+            <DropdownMenu>
+              <DropdownMenuTrigger asChild>
+                <button
+                  type="button"
+                  aria-label="Quick toggles"
+                  title="Quick toggles"
+                  className="inline-flex items-center justify-center size-6 rounded text-muted-foreground hover:bg-muted hover:text-foreground"
+                >
+                  <Plus className="size-3.5" />
+                </button>
+              </DropdownMenuTrigger>
+              <DropdownMenuContent align="start">
+                <DropdownMenuItem
+                  onSelect={async () => {
+                    // v1.9: tri-state collapses to two on the wire when toggled
+                    // here. null (inherit) treated as off; click flips to true.
+                    // To restore "inherit" the user opens SettingsPane.
+                    const next = webSearchEnabled === true ? false : true;
+                    try {
+                      await api.sessions.update(sessionId, { web_search_enabled: next });
+                    } catch (err) {
+                      toast.error(err instanceof Error ? err.message : 'failed to toggle web search');
+                    }
+                  }}
+                  className="text-xs"
+                >
+                  <Check className={`size-3 ${webSearchEnabled === true ? 'opacity-100' : 'opacity-0'}`} />
+                  Web search
+                </DropdownMenuItem>
+              </DropdownMenuContent>
+            </DropdownMenu>
+          )}
         </div>
       )}
       <div className="px-4 py-3 flex items-end gap-2">