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.

spec/services/automation_rules/action_service_spec.rb

@@ -88,8 +88,31 @@ RSpec.describe AutomationRules::ActionService do
       end
     end
 
+    describe '#perform with remove assignment actions' do
+      let!(:team) { create(:team, account: account) }
+
+      before do
+        conversation.update!(assignee: agent, team: team)
+        rule.actions = [
+          { action_name: 'remove_assigned_agent', action_params: [] },
+          { action_name: 'remove_assigned_team', action_params: [] }
+        ]
+        rule.save!
+      end
+
+      it 'removes assignee and team from the conversation' do
+        described_class.new(rule, account, conversation).perform
+
+        expect(conversation.reload.assignee).to be_nil
+        expect(conversation.team).to be_nil
+      end
+    end
+
     describe '#perform with send_email_transcript action' do
       before do
+        allow(account).to receive(:email_transcript_enabled?).and_return(true)
+        allow(account).to receive(:within_email_rate_limit?).and_return(true)
+        allow(account).to receive(:increment_email_sent_count).and_return(true)
         rule.actions << { action_name: 'send_email_transcript', action_params: ['contact@example.com, agent@example.com,agent1@example.com'] }
         rule.save
       end