feat: Add 'None' option to remove assigned agents/teams in macros and automations

- Add 'None' option (with id: 'nil') to agent and team assignment dropdowns in macros
- Deprecate remove_assigned_team action in favor of assign_team with 'None' option
- Update helper functions to properly display 'None' for unassignment
- Add comprehensive test coverage for the new functionality
- Maintain backward compatibility with existing remove_assigned_team action

Fixes #7551

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/javascript/dashboard/routes/dashboard/settings/macros/constants.js

@@ -19,6 +19,8 @@ export const MACRO_ACTION_TYPES = [
     label: 'REMOVE_LABEL',
     inputType: 'multi_select',
   },
+  // @deprecated: Use assign_team with 'None' option instead
+  // Kept for backward compatibility
   {
     key: 'remove_assigned_team',
     label: 'REMOVE_ASSIGNED_TEAM',

app/javascript/dashboard/routes/dashboard/settings/macros/macroHelper.js

@@ -17,6 +17,7 @@ export const resolveActionName = key => {
 export const resolveTeamIds = (teams, ids) => {
   return ids
     .map(id => {
+      if (id === 'nil') return 'None';
       const team = teams.find(i => i.id === id);
       return team ? team.name : '';
     })
@@ -35,6 +36,8 @@ export const resolveLabels = (labels, ids) => {
 export const resolveAgents = (agents, ids) => {
   return ids
     .map(id => {
+      if (id === 'nil') return 'None';
+      if (id === 'self') return 'Self';
       const agent = agents.find(i => i.id === id);
       return agent ? agent.name : '';
     })