Release v3.8.33 (#4515)

Release v3.8.33 — full CHANGELOG in the PR body. Blocking gates green (Build, Lint, Unit Tests 8/8, Package Artifact, Quality Gates, Quality Ratchet, Docs Sync, PR Test Policy, test-vitest). Admin-merged over a Node 26 future-compat timer flake (1/4) + an E2E UI flake (3/9) — both verified non-deterministic; full test:unit validated locally (16936 pass).

src/shared/validation/compressionConfigSchemas.ts

@@ -195,6 +195,7 @@ export const compressionSettingsUpdateSchema = z
     ultra: ultraConfigSchema.optional(),
     contextEditing: contextEditingConfigSchema.optional(),
     engines: z.record(z.string(), engineToggleSchema).optional(),
+    enginesExplicit: z.boolean().optional(),
     activeComboId: z.string().nullable().optional(),
   })
   .strict();