normalizer: configurable float epsilon + JSON-path volatile mask scoping

Follow-ups to #4 normalizer PoC v2:
- Profile.float_decimals (default 6) flows into Rules.RoundFloatsInNode.
- mask_volatile_settings switches from name-only HashSet to a JSONPath-lite
  allowlist ($.a.b.c) so same-named fields in unrelated subtrees stay intact.
- default.yaml migrated; 6 new tests including a regression trap for the
  unrelated-subtree case. 16/16 normalizer tests, 77/77 solution tests.

Refs #2

src/Recordingtest.Normalizer/Normalizer.cs

@@ -92,7 +92,8 @@ public static class Normalizer
                 {
                     if (isJson && jsonNode is not null)
                     {
-                        var (n, c) = Rules.RoundFloatsInNode(jsonNode);
+                        var decimals = profile.FloatDecimals ?? Rules.DefaultFloatDecimals;
+                        var (n, c) = Rules.RoundFloatsInNode(jsonNode, decimals);
                         jsonNode = n;
                         log.Add(new RuleApplication(rule, c));
                     }
@@ -106,7 +107,10 @@ public static class Normalizer
                 {
                     if (isJson && jsonNode is not null)
                     {
-                        var (n, c) = Rules.MaskVolatileSettings(jsonNode);
+                        var paths = (profile.MaskVolatileSettings is { Count: > 0 })
+                            ? (IReadOnlyList<string>)profile.MaskVolatileSettings
+                            : Rules.DefaultVolatileSettingPaths;
+                        var (n, c) = Rules.MaskVolatileSettings(jsonNode, paths);
                         jsonNode = n;
                         log.Add(new RuleApplication(rule, c));
                     }

src/Recordingtest.Normalizer/Profile.cs

@@ -8,6 +8,19 @@ public sealed class Profile
     public string Name { get; set; } = "";
     public List<string> Rules { get; set; } = new();
 
+    /// <summary>
+    /// Optional float decimals for round_floats. Null means use default (6).
+    /// </summary>
+    [YamlMember(Alias = "float_decimals", ApplyNamingConventions = false)]
+    public int? FloatDecimals { get; set; }
+
+    /// <summary>
+    /// Optional JSON-path allowlist for mask_volatile_settings.
+    /// Each entry is a JSONPath-lite string like "$.GridSnap" or "$.Viewport.GridColor.R".
+    /// </summary>
+    [YamlMember(Alias = "mask_volatile_settings", ApplyNamingConventions = false)]
+    public List<string>? MaskVolatileSettings { get; set; }
+
     public static Profile Load(string profileName)
     {
         var baseDir = AppContext.BaseDirectory;
@@ -22,6 +35,7 @@ public sealed class Profile
         var yaml = File.ReadAllText(path);
         var deserializer = new DeserializerBuilder()
             .WithNamingConvention(CamelCaseNamingConvention.Instance)
+            .IgnoreUnmatchedProperties()
             .Build();
         return deserializer.Deserialize<Profile>(yaml) ?? new Profile { Name = profileName };
     }

src/Recordingtest.Normalizer/Rules.cs

@@ -94,7 +94,12 @@ public static class Rules
     /// JSON-aware: parse and round all double values to 6 decimals. Operates only when input is JSON.
     /// Returns (json-output, count) when input is JSON; otherwise returns input unchanged with count=0.
     /// </summary>
+    public const int DefaultFloatDecimals = 6;
+
     public static (JsonNode? node, int count) RoundFloatsInNode(JsonNode? node)
+        => RoundFloatsInNode(node, DefaultFloatDecimals);
+
+    public static (JsonNode? node, int count) RoundFloatsInNode(JsonNode? node, int decimals)
     {
         int count = 0;
         if (node is null) return (null, 0);
@@ -109,7 +114,7 @@ public static class Rules
                 {
                     if (kv.Value is JsonValue v && TryAsDouble(v, out var d, out var wasFloat) && wasFloat)
                     {
-                        var rounded = Math.Round(d, 6, MidpointRounding.AwayFromZero);
+                        var rounded = Math.Round(d, decimals, MidpointRounding.AwayFromZero);
                         obj[kv.Key] = JsonValue.Create(rounded);
                         count++;
                     }
@@ -126,7 +131,7 @@ public static class Rules
                     var item = arr[i];
                     if (item is JsonValue v && TryAsDouble(v, out var d, out var wasFloat) && wasFloat)
                     {
-                        var rounded = Math.Round(d, 6, MidpointRounding.AwayFromZero);
+                        var rounded = Math.Round(d, decimals, MidpointRounding.AwayFromZero);
                         arr[i] = JsonValue.Create(rounded);
                         count++;
                     }
@@ -164,45 +169,104 @@ public static class Rules
     }
 
     /// <summary>
-    /// Allowlist of field names whose values are known to be volatile boolean/scalar
-    /// settings (per docs/sut-catalog/json-configs.json). The values are replaced with
-    /// a deterministic placeholder so golden-file comparisons stay stable while still
-    /// preserving the field's presence and key order.
+    /// Default JSON-path allowlist for known volatile fields, used when a profile
+    /// does not specify its own list. Each entry is a JSONPath-lite string anchored
+    /// at the document root.
     /// </summary>
-    public static readonly HashSet<string> VolatileSettingFieldNames = new(StringComparer.Ordinal)
+    public static readonly IReadOnlyList<string> DefaultVolatileSettingPaths = new List<string>
     {
-        "CanOverrideWireColorWithFace",
-        "IsSidePanelVisible",
-        "OverrideFaceColor",
-        "Solar_IsLocalTime",
-        "VisibleGrid",
-        "GridSnap",
-        "MidpointOsnap",
-        "GridSpacing",
-        "GridColor.ALPHA",
-        "GridColor.BLUE",
-        "GridColor.GREEN",
-        "GridColor.RED",
-        "MajorGridColor.ALPHA",
-        "MajorGridColor.BLUE",
-        "MajorGridColor.GREEN",
-        "MajorGridColor.RED",
+        "$.CanOverrideWireColorWithFace",
+        "$.IsSidePanelVisible",
+        "$.OverrideFaceColor",
+        "$.Solar_IsLocalTime",
+        "$.VisibleGrid",
+        "$.GridSnap",
+        "$.MidpointOsnap",
+        "$.GridSpacing",
+        "$.GridColor.ALPHA",
+        "$.GridColor.BLUE",
+        "$.GridColor.GREEN",
+        "$.GridColor.RED",
+        "$.MajorGridColor.ALPHA",
+        "$.MajorGridColor.BLUE",
+        "$.MajorGridColor.GREEN",
+        "$.MajorGridColor.RED",
     };
 
+    /// <summary>
+    /// Parses a JSONPath-lite string of the form "$.a.b.c" into segment list ["a","b","c"].
+    /// Throws on malformed input. Wildcards and array indexers are not supported.
+    /// </summary>
+    public static List<string> ParseJsonPathLite(string path)
+    {
+        if (string.IsNullOrWhiteSpace(path))
+            throw new ArgumentException("path is empty", nameof(path));
+        if (!path.StartsWith("$"))
+            throw new ArgumentException($"path must start with '$': {path}", nameof(path));
+        var segments = new List<string>();
+        var rest = path.Substring(1);
+        if (rest.Length == 0) return segments;
+        if (rest[0] != '.')
+            throw new ArgumentException($"path must continue with '.': {path}", nameof(path));
+        // split on '.' but preserve empties as errors
+        var parts = rest.Substring(1).Split('.');
+        foreach (var p in parts)
+        {
+            if (string.IsNullOrEmpty(p))
+                throw new ArgumentException($"empty segment in path: {path}", nameof(path));
+            if (p.Contains('*') || p.Contains('[') || p.Contains(']'))
+                throw new ArgumentException($"wildcards/indexers not supported: {path}", nameof(path));
+            segments.Add(p);
+        }
+        return segments;
+    }
+
     public static (JsonNode? node, int count) MaskVolatileSettings(JsonNode? node)
+        => MaskVolatileSettings(node, DefaultVolatileSettingPaths);
+
+    public static (JsonNode? node, int count) MaskVolatileSettings(JsonNode? node, IReadOnlyList<string> jsonPaths)
     {
         int count = 0;
         if (node is null) return (null, 0);
+
+        // Pre-parse the allowlist into segment chains for exact matching.
+        var allow = new List<List<string>>(jsonPaths.Count);
+        foreach (var p in jsonPaths)
+        {
+            allow.Add(ParseJsonPathLite(p));
+        }
+
+        var stack = new List<string>();
         Walk(node);
         return (node, count);
 
+        bool PathMatches()
+        {
+            foreach (var chain in allow)
+            {
+                if (chain.Count != stack.Count) continue;
+                bool eq = true;
+                for (int i = 0; i < chain.Count; i++)
+                {
+                    if (!string.Equals(chain[i], stack[i], StringComparison.Ordinal))
+                    {
+                        eq = false;
+                        break;
+                    }
+                }
+                if (eq) return true;
+            }
+            return false;
+        }
+
         void Walk(JsonNode n)
         {
             if (n is JsonObject obj)
             {
                 foreach (var kv in obj.ToList())
                 {
-                    if (VolatileSettingFieldNames.Contains(kv.Key))
+                    stack.Add(kv.Key);
+                    if (PathMatches())
                     {
                         obj[kv.Key] = JsonValue.Create("<VOLATILE>");
                         count++;
@@ -211,6 +275,7 @@ public static class Rules
                     {
                         Walk(kv.Value);
                     }
+                    stack.RemoveAt(stack.Count - 1);
                 }
             }
             else if (n is JsonArray arr)

src/Recordingtest.Normalizer/profiles/default.yaml

@@ -1,4 +1,5 @@
 name: default
+float_decimals: 6
 rules:
   - strip_timestamps
   - mask_guids
@@ -6,3 +7,20 @@ rules:
   - round_floats
   - mask_volatile_settings
   - sort_json_keys
+mask_volatile_settings:
+  - "$.CanOverrideWireColorWithFace"
+  - "$.IsSidePanelVisible"
+  - "$.OverrideFaceColor"
+  - "$.Solar_IsLocalTime"
+  - "$.VisibleGrid"
+  - "$.GridSnap"
+  - "$.MidpointOsnap"
+  - "$.GridSpacing"
+  - "$.GridColor.ALPHA"
+  - "$.GridColor.BLUE"
+  - "$.GridColor.GREEN"
+  - "$.GridColor.RED"
+  - "$.MajorGridColor.ALPHA"
+  - "$.MajorGridColor.BLUE"
+  - "$.MajorGridColor.GREEN"
+  - "$.MajorGridColor.RED"