🛡️ refactor: Scope Action Mutations by Parent Resource Ownership (#12237)

* 🛡️ fix: Scope action mutations by parent resource ownership

Prevent cross-tenant action overwrites by validating that an existing
action's agent_id/assistant_id matches the URL parameter before allowing
updates or deletes. Without this, a user with EDIT access on their own
agent could reference a foreign action_id to hijack another agent's
action record.

* 🛡️ fix: Harden action ownership checks and scope write filters

- Remove && short-circuit that bypassed the guard when agent_id or
  assistant_id was falsy (e.g. assistant-owned actions have no agent_id,
  so the check was skipped entirely on the agents route).
- Include agent_id / assistant_id in the updateAction and deleteAction
  query filters so the DB write itself enforces ownership atomically.
- Log a warning when deleteAction returns null (silent no-op from
  data-integrity mismatch).

* 📝 docs: Update Action model JSDoc to reflect scoped query params

* ✅ test: Add Action ownership scoping tests

Cover update, delete, and cross-type protection scenarios using
MongoMemoryServer to verify that scoped query filters (agent_id,
assistant_id) prevent cross-tenant overwrites and deletions at the
database level.

* 🛡️ fix: Scope updateAction filter in agent duplication handler

* 🐛 fix: Use action metadata domain instead of action_id when duplicating agent actions

The duplicate handler was splitting `action.action_id` by `actionDelimiter`
to extract the domain, but `action_id` is a bare nanoid that doesn't
contain the delimiter. This produced malformed entries in the duplicated
agent's actions array (nanoid_action_newNanoid instead of
domain_action_newNanoid). The domain is available on `action.metadata.domain`.

* ✅ test: Add integration tests for agent duplication action handling

Uses MongoMemoryServer with real Agent and Action models to verify:
- Duplicated actions use metadata.domain (not action_id) for the
  agent actions array entries
- Sensitive metadata fields are stripped from duplicated actions
- Original action documents are not modified

api/server/controllers/agents/v1.js

@@ -371,7 +371,7 @@ const duplicateAgentHandler = async (req, res) => {
      */
     const duplicateAction = async (action) => {
       const newActionId = nanoid();
-      const [domain] = action.action_id.split(actionDelimiter);
+      const { domain } = action.metadata;
       const fullActionId = `${domain}${actionDelimiter}${newActionId}`;
 
       // Sanitize sensitive metadata before persisting
@@ -381,7 +381,7 @@ const duplicateAgentHandler = async (req, res) => {
       }
 
       const newAction = await updateAction(
-        { action_id: newActionId },
+        { action_id: newActionId, agent_id: newAgentId },
         {
           metadata: filteredMetadata,
           agent_id: newAgentId,