fix: keep supervisor controls usable and prevent overlapping reviews

Allow only one active review across manual starts, automatic runs and resume. Add cancellation that holds admission through runtime cleanup, preserves saved batches and prevents cancelled runs from resuming.

Keep review controls usable during execution, show a dismissible progress notice and remove redundant filter labels. Include focused regressions and lifecycle documentation.

Release note: Supervision reviews can now be cancelled from Activity records. Starting another review shows the active review instead of duplicating work, while scope, time and refresh controls remain available.

tests/support/supervisor-layout-regression.tsx

@@ -146,6 +146,7 @@ Object.defineProperty(window, 'goodbuddy', {
       ? {}
       : {
           supervision: {
+            execution: async () => ({ active: params.has('activity'), ...(params.has('activity') ? { runId: 'activity-1' } : {}) }),
             batches: async ({ runId, offset, limit }: { runId: string; offset: number; limit: number }) => Array.from({ length: runId === 'activity-0' ? 6 : 12 }, (_, index) => ({
               id: `leaf-${index}`, projectId: index < 3 ? 'Atlas' : 'Beacon', conversationId: `conversation-${Math.floor(index / 2)}`,
               evidence: [{ id: `source-${index}`, sourceType: 'conversation', sourceId: `conversation-${Math.floor(index / 2)}`,
@@ -156,7 +157,7 @@ Object.defineProperty(window, 'goodbuddy', {
                 changeDigest: '已补充负责人和待核对项。', openItems: ['核对外部评审日期。'],
                 events: [{ title: '验收安排', description: '先核对资料，再确认交付日期。', sourceReferenceIds: [`source-${index}`] }], entities: [], entityChanges: [], relations: [] }
             })).slice(offset, offset + limit),
-            resume: async () => {}, pause: async () => {},
+             resume: async () => {}, pause: async () => {}, cancel: async () => {},
             activity: async (input?: { configId?: string }) => ['running', 'failed', 'completed'].map((status, index) => ({
               id: `activity-${index}`, kind: index === 2 ? 'supervision' : 'heartbeat', trigger: index === 2 ? 'manual' : 'scheduled', status,
               scope: { kind: 'global' }, startedAt: '2026-09-23T08:00:00Z', completedAt: status === 'running' ? null : '2026-09-23T08:01:00Z',