fix(maestro): restore sidebar footer, fix spawn modal and session card regressions

Post-React-migration regressions: spawn submit button moved to modal
footer, sidebar footer restored (help/theme/palette/status/spawn),
session card stripped of redundant Tailwind, action buttons use proper
leaf-act/leaf-actions CSS structure for hover-only visibility.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/components/spawn/SpawnModal.tsx

@@ -64,16 +64,23 @@ export function SpawnModal({ seed, onSuccess, onClose }: SpawnModalProps) {
           </button>
         </header>
         <div ref={filterInputRef} className="min-h-0 flex-1 overflow-auto">
-          <SpawnForm seed={seed} onSuccess={handleSuccess} />
+          <SpawnForm seed={seed} onSuccess={handleSuccess} externalSubmit />
         </div>
         <div className="flex justify-end gap-sp-2 border-t border-border p-sp-3">
           <button
             type="button"
-            className="rounded-r-1 border border-border px-sp-3 py-sp-1 text-fs-12 text-ink"
+            className="rounded-r-1 border border-border px-sp-3 py-sp-1 text-fs-13 text-ink"
             onClick={onClose}
           >
             Cancel
           </button>
+          <button
+            type="submit"
+            form="spawn-form"
+            className="btn btn-primary rounded-r-1 px-sp-4 py-sp-1 text-fs-13 font-semibold"
+          >
+            Spawn
+          </button>
         </div>
       </div>
     </div>,