fix: add explicit remove assignment actions to macros and automations (#12172)

This updates macros and automations so agents can explicitly remove
assigned agents or teams, while keeping the existing `Assign -> None`
flow working for backward compatibility.

Fixes: #7551
Closes: #7551

## Why
The original macro change exposed unassignment only through `Assign ->
None`, which made macros behave differently from automations and left
the explicit remove actions inconsistent across the product. This keeps
the lower-risk compatibility path and adds the explicit remove actions
requested in review.

## What this change does
- Adds `Remove Assigned Agent` and `Remove Assigned Team` as explicit
actions in macros.
- Adds the same explicit remove actions in automations.
- Keeps `Assign Agent -> None` and `Assign Team -> None` working for
existing behavior and stored payloads.
- Preserves backward compatibility for existing macro and automation
execution payloads.
- Downmerges the latest `develop` and resolves the conflicts while
keeping both the new remove actions and current `develop` behavior.

## Validation
- Verified both remove actions are available and selectable in the macro
editor.
- Verified both remove actions are available and selectable in the
automation builder.
- Applied a disposable macro with `Remove Assigned Agent` and `Remove
Assigned Team` on a real conversation and confirmed both fields were
cleared.
- Applied a disposable macro with `Assign Agent -> None` and `Assign
Team -> None` on a real conversation and confirmed both fields were
still cleared.

app/models/automation_rule.rb

@@ -40,9 +40,10 @@ class AutomationRule < ApplicationRecord
   end
 
   def actions_attributes
-    %w[send_message add_label remove_label send_email_to_team assign_team assign_agent send_webhook_event mute_conversation
-       send_attachment change_status resolve_conversation open_conversation pending_conversation snooze_conversation change_priority
-       send_email_transcript add_private_note].freeze
+    %w[send_message add_label remove_label send_email_to_team assign_team assign_agent remove_assigned_agent
+       remove_assigned_team send_webhook_event mute_conversation send_attachment change_status resolve_conversation
+       open_conversation pending_conversation snooze_conversation change_priority send_email_transcript
+       add_private_note].freeze
   end
 
   def file_base_data

app/models/macro.rb

@@ -30,9 +30,9 @@ class Macro < ApplicationRecord
 
   validate :json_actions_format
 
-  ACTIONS_ATTRS = %w[send_message add_label assign_team assign_agent mute_conversation change_status remove_label remove_assigned_team
-                     resolve_conversation snooze_conversation change_priority send_email_transcript send_attachment
-                     add_private_note send_webhook_event].freeze
+  ACTIONS_ATTRS = %w[send_message add_label assign_team assign_agent mute_conversation change_status remove_label remove_assigned_agent
+                     remove_assigned_team resolve_conversation snooze_conversation change_priority send_email_transcript
+                     send_attachment add_private_note send_webhook_event].freeze
 
   def set_visibility(user, params)
     self.visibility = params[:visibility]