feat(scripts): read-only, allow-listed Files global for site scripts; Delmia test receiver parses recipe files

Script file access (design docs/plans/2026-09-28-script-file-access-design.md): Files.ReadTextAsync /
ReadLinesAsync / ExistsAsync on site ScriptGlobals (+ Instance.Files), backed by the site-singleton
ScriptFileReader. The one host-mediated exception to the System.IO ban - scripts still never name a
System.IO type. OFF by default: ScadaBridge:SiteRuntime:ScriptFileAccess:AllowedRoots (empty = every call
throws Disabled) + MaxFileBytes (1 MiB, validated 1..64 MiB, roots must be absolute). Guard: fully
qualified, no device paths / ADS, canonical path strictly inside a root (directory-boundary match), no
reparse point on the file or any directory below the root, size cap before and during the read.
Errors are one Commons type, ScriptFileAccessException(+ScriptFileAccessFailure); Commons.Types.Scripts
joins the default script imports on every surface so it binds by short name. Mirrored on
ScriptCompileSurface (CompileFiles, parity-pinned) and the Test Run sandbox (binds, refuses Disabled).
Inbound (central) scripts do not get it.

Rig: docker/recipes (sample RecipeValueName,RecipeValue files incl. an invalid one) bind-mounted
read-only at /app/recipes on both site-a nodes with AllowedRoots [/app/recipes]. The TestMesMachine
SimDelmiaRecipe simulator now reads + parses the downloaded file, converts each value to its recipe tag's
type and loads it all-or-nothing (14 new TestDelmiaReceiver attributes); verify-mes-test-machine.sh
group A covers accept / re-download / invalid lines / NotFound / OutsideAllowedRoots, VERIFY_GROUPS
selects groups (rig: AD).

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/SiteRuntimeOptionsValidator.cs

@@ -119,5 +119,17 @@ public sealed class SiteRuntimeOptionsValidator : OptionsValidatorBase<SiteRunti
             $"(was {options.MaxLogLinesPerRun}); it is the per-run cap on Flow Debugger ScriptLog " +
             "rows a script's Log.* calls may produce (design 2026-09-09 D7), and a run that may " +
             "emit no lines at all cannot report its own truncation.");
+
+        var files = options.ScriptFileAccess ?? new Scripts.ScriptFileAccessOptions();
+        builder.RequireThat(files.MaxFileBytes > 0 && files.MaxFileBytes <= Scripts.ScriptFileAccessOptions.MaxFileBytesCeiling,
+            $"ScadaBridge:SiteRuntime:ScriptFileAccess:MaxFileBytes must be between 1 and " +
+            $"{Scripts.ScriptFileAccessOptions.MaxFileBytesCeiling} (was {files.MaxFileBytes}); it caps one Files.* read.");
+        for (var i = 0; i < files.AllowedRoots.Count; i++)
+        {
+            var root = files.AllowedRoots[i];
+            builder.RequireThat(!string.IsNullOrWhiteSpace(root) && System.IO.Path.IsPathFullyQualified(root),
+                $"ScadaBridge:SiteRuntime:ScriptFileAccess:AllowedRoots:{i} must be an absolute directory path " +
+                $"(was '{root}'); a relative root would resolve against the service's working directory.");
+        }
     }
 }