Add FLUID wire contract schemas

Nine JSON Schemas covering the five record types from the schema spec,
plus backend requirements, feedback, the revision descriptor, routing
policy and the telemetry envelope. These are the integration boundary:
readable without any fluid-core code, so adapters may be written in any
language.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014KmVxhJ35tCo7rE7UnLwWu

Assistant: claude-code
Assistant-Model: opus
Assistant-Process: 1116572@bnt-lap001
Assistant-Session: 8ba9bb93-a72a-4883-b189-2499cce5c400

schemas/event.schema.json

@@ -0,0 +1,35 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://fluid.dev/schemas/event.schema.json",
+  "title": "FLUID audit event",
+  "description": "Append-only record of a material lifecycle transition. FLUID evolution is itself a system behavior that must remain reconstructable (FluidHypothesisRevisionSchema.md section 15).",
+  "type": "object",
+  "properties": {
+    "fluid_event": {
+      "type": "object",
+      "properties": {
+        "schema_version": { "$ref": "common.schema.json#/$defs/schemaVersion" },
+        "id": { "$ref": "common.schema.json#/$defs/eventId" },
+        "occurred_at": { "$ref": "common.schema.json#/$defs/timestamp" },
+        "entity_type": { "enum": ["pressure", "hypothesis", "revision", "experiment", "backend_requirement", "intent", "decision", "routing_policy"] },
+        "entity_id": { "type": "string", "minLength": 1 },
+        "event_type": { "type": "string", "minLength": 1 },
+        "actor": { "$ref": "common.schema.json#/$defs/actor" },
+        "inputs": {
+          "type": "array",
+          "items": { "type": "string" },
+          "description": "Identifiers of the records this transition drew on."
+        },
+        "reason": { "type": "string" },
+        "evidence_refs": {
+          "type": "array",
+          "items": { "$ref": "common.schema.json#/$defs/evidenceRef" }
+        }
+      },
+      "required": ["schema_version", "id", "occurred_at", "entity_type", "entity_id", "event_type", "actor"],
+      "additionalProperties": false
+    }
+  },
+  "required": ["fluid_event"],
+  "additionalProperties": false
+}