feat: add strict legacy probe override schema

Launcher.Next.Application/LegacyProbeOverride.cs

@@ -0,0 +1,39 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace Launcher.Next.Application;
+
+public sealed record LegacyProbeOverride(
+    int SchemaVersion,
+    string Mode,
+    string SettingsXml,
+    string DownloadListXml,
+    string CompatibilityOverlay,
+    string SelectedPattern,
+    string EvidenceOutputRoot);
+
+public static class LegacyProbeOverrideParser
+{
+    private static readonly JsonSerializerOptions Options = new()
+    {
+        PropertyNameCaseInsensitive = true,
+        UnmappedMemberHandling = JsonUnmappedMemberHandling.Disallow
+    };
+
+    public static LegacyProbeOverride Parse(string json)
+    {
+        try
+        {
+            var value = JsonSerializer.Deserialize<LegacyProbeOverride>(json, Options)
+                ?? throw new InvalidOperationException("LEGACY_PROBE_OVERRIDE_MISSING");
+            if (value.SchemaVersion != 1) throw new InvalidOperationException("LEGACY_PROBE_OVERRIDE_SCHEMA_UNSUPPORTED");
+            if (!string.Equals(value.Mode, "LegacyConfigurationProbe", StringComparison.Ordinal)) throw new InvalidOperationException("LEGACY_PROBE_MODE_REQUIRED");
+            if (new[] { value.SettingsXml, value.DownloadListXml, value.CompatibilityOverlay, value.SelectedPattern, value.EvidenceOutputRoot }.Any(string.IsNullOrWhiteSpace))
+                throw new InvalidOperationException("LEGACY_PROBE_INPUT_MISSING");
+            if (new[] { value.SettingsXml, value.DownloadListXml, value.CompatibilityOverlay, value.EvidenceOutputRoot }.Any(x => Uri.TryCreate(x, UriKind.Absolute, out var uri) && !uri.IsFile || x.Contains('*') || x.Contains('?')))
+                throw new InvalidOperationException("LEGACY_PROBE_INPUT_PATH_INVALID");
+            return value;
+        }
+        catch (JsonException) { throw new InvalidOperationException("LEGACY_PROBE_OVERRIDE_UNKNOWN_FIELD"); }
+    }
+}

tests/Launcher.Next.Tests/RosterAdaptersTests.cs

@@ -49,6 +49,15 @@ public sealed class RosterAdaptersTests
         Assert.Equal(["legacy-a"], selection.PluginIds);
     }
 
+    [Fact]
+    public void LegacyProbeOverride_RequiresExplicitProbeModeAndStrictSchema()
+    {
+        const string valid = """{"schemaVersion":1,"mode":"LegacyConfigurationProbe","settingsXml":"C:/Settings.xml","downloadListXml":"C:/download_list.xml","compatibilityOverlay":"C:/overlay.json","selectedPattern":"Plant","evidenceOutputRoot":"C:/evidence"}""";
+        Assert.Equal("Plant", LegacyProbeOverrideParser.Parse(valid).SelectedPattern);
+        Assert.Throws<InvalidOperationException>(() => LegacyProbeOverrideParser.Parse(valid.Replace("LegacyConfigurationProbe","Production")));
+        Assert.Throws<InvalidOperationException>(() => LegacyProbeOverrideParser.Parse(valid[..^1] + ",\"unknown\":true}"));
+    }
+
     [Fact]
     public void ProjectRoster_HasPriorityOverLegacy()
     {