fix(compression): allow enginesExplicit through PUT validation schema (#4532)

Adds enginesExplicit to the strict compression PUT schema so the panel can save without a 400. Kept only this commit; the Hub-render commit was superseded by Phase 2 (#4521) which rewrote CompressionHub.tsx. Does not reopen the Phase 1 gate (enginesExplicit is recomputed from stored engines, the persisted row is ignored). Tested.

Integrated into release/v3.8.33.

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();