refactor(admin): split whistleblower page.tsx + restore scope helpers

Whistleblower (1220 -> 349 LOC) split into 6 colocated components:
TabNavigation, StatCard, FilterBar, ReportCard, WhistleblowerCreateModal,
CaseDetailPanel. All under the 300 LOC soft target.

Drive-by fix: the earlier fc6a330 split of compliance-scope-types.ts
dropped several helper exports that downstream consumers still import
(lib/sdk/index.ts, compliance-scope-engine.ts, obligations page,
compliance-scope page, constraint-enforcer, drafting-engine validate).
Restored them in the appropriate domain modules:

- core-levels.ts: maxDepthLevel, getDepthLevelNumeric, depthLevelFromNumeric
- state.ts: createEmptyScopeState
- decisions.ts: createEmptyScopeDecision + ApplicableRegulation,
  RegulationObligation, RegulationAssessmentResult, SupervisoryAuthorityInfo

Verification: next build clean (142 pages generated), /sdk/whistleblower
still builds at ~11.5 kB.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

admin-compliance/app/sdk/whistleblower/_components/TabNavigation.tsx

@@ -0,0 +1,54 @@
+'use client'
+
+import React from 'react'
+
+export type TabId = 'overview' | 'new_reports' | 'investigation' | 'closed' | 'settings'
+
+export interface Tab {
+  id: TabId
+  label: string
+  count?: number
+  countColor?: string
+}
+
+export function TabNavigation({
+  tabs,
+  activeTab,
+  onTabChange
+}: {
+  tabs: Tab[]
+  activeTab: TabId
+  onTabChange: (tab: TabId) => void
+}) {
+  return (
+    <div className="border-b border-gray-200">
+      <nav className="flex gap-1 -mb-px" aria-label="Tabs">
+        {tabs.map(tab => (
+          <button
+            key={tab.id}
+            onClick={() => onTabChange(tab.id)}
+            className={`
+              px-4 py-3 text-sm font-medium border-b-2 transition-colors
+              ${activeTab === tab.id
+                ? 'border-purple-600 text-purple-600'
+                : 'border-transparent text-gray-500 hover:text-gray-700 hover:border-gray-300'
+              }
+            `}
+          >
+            <span className="flex items-center gap-2">
+              {tab.label}
+              {tab.count !== undefined && tab.count > 0 && (
+                <span className={`
+                  px-2 py-0.5 text-xs rounded-full
+                  ${tab.countColor || 'bg-gray-100 text-gray-600'}
+                `}>
+                  {tab.count}
+                </span>
+              )}
+            </span>
+          </button>
+        ))}
+      </nav>
+    </div>
+  )
+}