fix(protocol): align trace schemas with v2/v3 classify rules

RecordedTrace validation now follows classify_value — numeric version
selects v3, otherwise v2 — so mixed pages/states and v2 envelopes with
a version field fail Schema checks before Recall import. Keep standalone
trace_step as a v2|v3 union for tools that validate a single step.

crates/bsk-protocol/schema/trace_v2.json

@@ -1,7 +1,7 @@
 {
   "$schema": "http://json-schema.org/draft-07/schema#",
   "title": "TraceV2",
-  "description": "Persisted user-action trace exported by legacy `tool.record_stop` / `await`.\n\nUnknown extension fields are ignored so older traces remain readable. Mixed v2/v3 envelopes are rejected by `RecordedTrace` classification.",
+  "description": "Persisted user-action trace exported by legacy `tool.record_stop` / `await`.\n\nUnknown extension fields are ignored so older traces remain readable. `states[]` and a numeric `version` are reserved for Trace v3 / `RecordedTrace` classification.",
   "type": "object",
   "required": [
     "entry",
@@ -35,11 +35,18 @@
         "null"
       ]
     },
+    "states": false,
     "steps": {
       "type": "array",
       "items": {
         "$ref": "#/definitions/StepV2"
       }
+    },
+    "version": {
+      "description": "Numeric version selects Trace v3. Legacy v2 envelopes omit this field.",
+      "not": {
+        "type": "integer"
+      }
     }
   },
   "definitions": {