style(desktop): hide search when there's nothing to search

Empty datasets no longer render a search field. Adds a `searchHidden` prop
to PageSearchShell (artifacts/skills/messaging) and gates cron + command
center sessions search on a non-empty list. The chat sidebar already did
this via showSessionSections.

apps/desktop/src/app/artifacts/index.tsx

@@ -501,6 +501,7 @@ export function ArtifactsView({ setStatusbarItemGroup: _setStatusbarItemGroup, .
     <PageSearchShell
       {...props}
       onSearchChange={setQuery}
+      searchHidden={counts.all === 0}
       searchPlaceholder="Search artifacts..."
       searchValue={query}
       tabs={

apps/desktop/src/app/command-center/index.tsx

@@ -300,7 +300,7 @@ export function CommandCenterView({
               </p>
             </div>
             <div className="flex shrink-0 items-center gap-2">
-              {section === 'sessions' && (
+              {section === 'sessions' && sessions.length > 0 && (
                 <SearchField
                   containerClassName="max-w-[40vw]"
                   onChange={next => setQuery(next)}

apps/desktop/src/app/cron/index.tsx

@@ -419,14 +419,16 @@ export function CronView({ onClose }: CronViewProps) {
   return (
     <OverlayView closeLabel="Close cron" onClose={onClose}>
       <div className="flex min-h-0 flex-1 flex-col pt-[calc(var(--titlebar-height)+0.5rem)]">
-        <div className="mx-auto flex w-full max-w-4xl items-center gap-2 px-4 pb-2">
-          <SearchField
-            containerClassName="max-w-[60vw]"
-            onChange={setQuery}
-            placeholder="Search cron jobs…"
-            value={query}
-          />
-        </div>
+        {totalCount > 0 && (
+          <div className="mx-auto flex w-full max-w-4xl items-center gap-2 px-4 pb-2">
+            <SearchField
+              containerClassName="max-w-[60vw]"
+              onChange={setQuery}
+              placeholder="Search cron jobs…"
+              value={query}
+            />
+          </div>
+        )}
         {!jobs ? (
           <PageLoader label="Loading cron jobs..." />
         ) : visibleJobs.length === 0 ? (

apps/desktop/src/app/messaging/index.tsx

@@ -347,6 +347,7 @@ export function MessagingView({ setStatusbarItemGroup: _setStatusbarItemGroup, .
     <PageSearchShell
       {...props}
       onSearchChange={setQuery}
+      searchHidden={(platforms?.length ?? 0) === 0}
       searchPlaceholder="Search messaging..."
       searchValue={query}
     >

apps/desktop/src/app/page-search-shell.tsx

@@ -12,6 +12,8 @@ interface PageSearchShellProps extends React.ComponentProps<'section'> {
   onSearchChange: (value: string) => void
   searchPlaceholder: string
   searchValue: string
+  /** Hide the search field when there's nothing to search (empty dataset). */
+  searchHidden?: boolean
 }
 
 export function PageSearchShell({
@@ -22,6 +24,7 @@ export function PageSearchShell({
   onSearchChange,
   searchPlaceholder,
   searchValue,
+  searchHidden = false,
   ...props
 }: PageSearchShellProps) {
   return (
@@ -46,19 +49,23 @@ export function PageSearchShell({
         (see app-shell.tsx), so window dragging still works here.
       */}
       <div className="shrink-0">
-        <div className="flex items-center gap-3 px-3 pb-2 pt-[calc(var(--titlebar-height)+0.5rem)]">
-          {tabs ? (
-            <div className="flex min-w-0 flex-1 flex-wrap items-center gap-x-2 gap-y-1">{tabs}</div>
-          ) : null}
-          <div className={cn('flex shrink-0 items-center', !tabs && 'flex-1')}>
-            <SearchField
-              containerClassName="max-w-[45vw]"
-              onChange={onSearchChange}
-              placeholder={searchPlaceholder}
-              value={searchValue}
-            />
+        {(tabs || !searchHidden) && (
+          <div className="flex items-center gap-3 px-3 pb-2 pt-[calc(var(--titlebar-height)+0.5rem)]">
+            {tabs ? (
+              <div className="flex min-w-0 flex-1 flex-wrap items-center gap-x-2 gap-y-1">{tabs}</div>
+            ) : null}
+            {!searchHidden && (
+              <div className={cn('flex shrink-0 items-center', !tabs && 'flex-1')}>
+                <SearchField
+                  containerClassName="max-w-[45vw]"
+                  onChange={onSearchChange}
+                  placeholder={searchPlaceholder}
+                  value={searchValue}
+                />
+              </div>
+            )}
           </div>
-        </div>
+        )}
         {filters ? (
           <div className="flex flex-wrap items-center gap-x-2 gap-y-1 px-3 pb-2">{filters}</div>
         ) : null}

apps/desktop/src/app/skills/index.tsx

@@ -197,6 +197,7 @@ export function SkillsView({ setStatusbarItemGroup: _setStatusbarItemGroup, ...p
         ) : undefined
       }
       onSearchChange={setQuery}
+      searchHidden={mode === 'skills' ? (skills?.length ?? 0) === 0 : (toolsets?.length ?? 0) === 0}
       searchPlaceholder={mode === 'skills' ? 'Search skills...' : 'Search toolsets...'}
       searchValue={query}
       tabs={