fix(web): drop the taskbar theme label, align window padding to p-2

- Taskbar: the theme toggle is icon-only now, matching the Settings
  button beside it. The theme name moves into the title/aria-label so
  an icon-only control still has an accessible name and the current
  theme stays discoverable on hover.
- Pages: Fleet, Knowledge, Learning, Ops and Signals used p-4 (or
  p-4 md:p-6) while Tasks used p-2, so windows didn't line up. All now
  p-2. App Store and Settings are deliberately untouched — they have no
  root padding, using a full-bleed header whose border spans the window;
  insetting them would break that.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/src/lib/components/desktop-shell/Taskbar.svelte

@@ -109,12 +109,12 @@
   <div class="flex shrink-0 items-center gap-0.5">
     <button
       type="button"
-      class="flex items-center justify-center gap-1.5 rounded-md p-1.5 text-muted-foreground hover:bg-muted hover:text-foreground"
+      class="flex items-center justify-center rounded-md p-1.5 text-muted-foreground hover:bg-muted hover:text-foreground"
       onclick={() => toggleTheme()}
-      title="Cycle theme"
+      title="Cycle theme ({THEME_LABELS[getTheme()]})"
+      aria-label="Cycle theme, currently {THEME_LABELS[getTheme()]}"
     >
       <PaletteIcon class="size-4" />
-      <span class="hidden text-xs sm:inline">{THEME_LABELS[getTheme()]}</span>
     </button>
     <button
       type="button"

web/src/pages/Knowledge.svelte

@@ -43,7 +43,7 @@
   }
 </script>
 
-<div class="flex h-full flex-col gap-4 p-4 md:p-6">
+<div class="flex h-full flex-col gap-4 p-2">
   <div class="flex items-center justify-between">
     <h1 class="text-lg font-semibold">Knowledge</h1>
   </div>

web/src/pages/KnowledgeBase.svelte

@@ -184,7 +184,7 @@
   })
 </script>
 
-<div class="flex h-full flex-col gap-3 p-4">
+<div class="flex h-full flex-col gap-3 p-2">
   <!-- single toolbar row: the search box is shared by both views (graph
        highlights nodes, table filters rows); the Inactive toggle + count are
        table-only; the graph/table switch sits inline on the right. -->

web/src/pages/Learning.svelte

@@ -79,7 +79,7 @@
   }
 </script>
 
-<div class="flex h-full flex-col gap-4 overflow-y-auto p-4 md:p-6">
+<div class="flex h-full flex-col gap-4 overflow-y-auto p-2">
   <h1 class="text-lg font-semibold">Learning</h1>
 
   <Card.Root>

web/src/pages/Ops.svelte

@@ -102,7 +102,7 @@
   ]
 </script>
 
-<div class="flex h-full flex-col gap-4 p-4 md:p-6">
+<div class="flex h-full flex-col gap-4 p-2">
   <h1 class="text-lg font-semibold">Operations ledger</h1>
 
   <Tabs.Root value="approvals" class="flex flex-1 flex-col overflow-hidden">

web/src/pages/Signals.svelte

@@ -98,7 +98,7 @@
   const columnsWithoutActions = makeColumns(false, null)
 </script>
 
-<div class="flex h-full flex-col gap-4 p-4 md:p-6">
+<div class="flex h-full flex-col gap-4 p-2">
   <div class="flex items-center justify-between">
     <h1 class="text-lg font-semibold">Signals</h1>
     <Select.Root type="single" bind:value={severityFilter}>