Defer server file changes until guarded restart activation

Persist beta, promotion, drift, and rollback payloads until occupancy and restart-capacity checks pass. Preserve rollback snapshots and campaign ordering, and allow held rollback campaigns to resume safely.

Fixes #28

Validation: 805 tests passed, Svelte checks clean, production build passed.

tests/unit/beta-promotion.test.ts

@@ -3,6 +3,7 @@ import { existsSync } from 'node:fs';
 import { readFile } from 'node:fs/promises';
 import { join } from 'node:path';
 import { newFixture, type Fixture } from '../helpers/fixture.js';
+import { activateFiles } from '../helpers/staged-files.js';
 
 let fixture: Fixture;
 const servers = ['t5_zombie_theater_1', 't5_zombie_cosmodrome_1'];
@@ -22,6 +23,7 @@ async function ready(kind: 'script' | 'baseline' = 'script', scope: 'game' | 'ma
         scopeType: scope, scopeValue: scope === 'game' ? 't5' : 'zombie_theater', content: Buffer.from(kind === 'script' ? 'main(){}' : 'set sv_voice "1"\n') });
     const version = getLatestVersion(script.id)!;
     const { betaId } = await openBeta({ scripts: [{ scriptId: script.id, scriptVersionId: version.id }], servers: [servers[0]], waitForHealth: false, waitForMatch: false });
+    await activateFiles('beta', betaId);
     db().prepare("UPDATE betas SET state = 'ready-promote' WHERE id = ?").run(betaId);
     db().prepare("UPDATE beta_servers SET stage = 'ready', restarted_at = ? WHERE beta_id = ?").run(new Date().toISOString(), betaId);
     return { betaId, script, version };
@@ -40,6 +42,8 @@ describe('reviewed beta promotion', () => {
         const result = await promoteBeta(betaId, preview.token);
         expect(result).toMatchObject({ awaitingActivation: 1, failedServers: [] });
         expect(result.deploymentId).toContain('promote');
+        expect(existsSync(destination())).toBe(false);
+        await activateFiles('campaign', result.deploymentId);
         expect(await readFile(destination(), 'utf8')).toBe('main(){}');
     });
     it('rejects changed scope membership before creating a campaign or writing extra files', async () => {