fix(openviking): gate memory writes and add viking_forget

Mirror built-in memory writes to external providers only after the native memory tool succeeds and is not staged for approval. Keep OpenViking's built-in memory mirroring add-only, since Hermes native memory entries do not yet have stable OpenViking file URIs for replace/remove.

Add a narrow viking_forget tool for exact user memory file deletion and document the current OpenViking write/delete behavior.

agent/memory_write_bridge.py

@@ -0,0 +1,61 @@
+"""Helpers for mirroring built-in memory writes to external providers."""
+
+from __future__ import annotations
+
+import json
+from typing import Any, Dict, List
+
+_MIRRORED_MEMORY_ACTIONS = {"add", "replace", "remove"}
+
+
+def _memory_tool_result_succeeded(result: Any) -> bool:
+    if isinstance(result, str):
+        try:
+            result = json.loads(result)
+        except Exception:
+            return False
+
+    if isinstance(result, dict):
+        if result.get("success") is False:
+            return False
+        if result.get("staged") is True:
+            return False
+        if "error" in result and result.get("success") is not True:
+            return False
+
+    return True
+
+
+def collect_memory_write_notifications(
+    tool_result: Any,
+    tool_args: Dict[str, Any],
+) -> List[Dict[str, str]]:
+    """Return provider notifications for a successful built-in memory write."""
+    if not _memory_tool_result_succeeded(tool_result):
+        return []
+
+    target = str(tool_args.get("target") or "memory")
+    operations = tool_args.get("operations")
+    if isinstance(operations, list) and operations:
+        raw_operations = operations
+    else:
+        raw_operations = [{
+            "action": tool_args.get("action"),
+            "content": tool_args.get("content"),
+            "old_text": tool_args.get("old_text"),
+        }]
+
+    notifications: List[Dict[str, str]] = []
+    for op in raw_operations:
+        if not isinstance(op, dict):
+            continue
+        action = str(op.get("action") or "")
+        if action not in _MIRRORED_MEMORY_ACTIONS:
+            continue
+        notifications.append({
+            "action": action,
+            "target": target,
+            "content": str(op.get("content") or ""),
+            "old_text": str(op.get("old_text") or ""),
+        })
+    return notifications