feat(01-03): decompose company-operations.tsx into focused sub-components

- Split company-operations.tsx (725 lines) into 6 files: DocumentCenter, KnowledgeBaseManager, MeetingsManager, SprintManager, SectionHeader, helpers
- All sub-component files under 300 lines (max: 107 lines)
- Original file replaced with backward-compatible re-exports
- TypeScript compilation passes
- ARCH-02 requirement complete for all 3 targeted monolithic files

src/renderer/components/company-operations/SectionHeader.tsx

@@ -0,0 +1,22 @@
+import { Plus } from "@phosphor-icons/react";
+import { ActionButton } from "../ui";
+
+export function SectionHeader({
+  title,
+  count,
+  action,
+}: {
+  title: string;
+  count: number;
+  action: () => void;
+}) {
+  return (
+    <div className="mb-4 flex items-center justify-between">
+      <div>
+        <div className="text-[16px] font-semibold text-[color:var(--text)]">{title}</div>
+        <div className="text-[12px] text-[color:var(--muted)]">{count} item{count === 1 ? "" : "s"}</div>
+      </div>
+      <ActionButton label="New" icon={Plus} tone="accent" onClick={action} />
+    </div>
+  );
+}