fix: align AgentBot ownership with conversation counts (#15343)

AgentBot-owned conversations are now treated as assigned across
conversation lists, counts, pagination, permissions, unread membership,
human auto-assignment, and advanced assignee filters.

## Closes

-
https://linear.app/chatwoot/issue/CW-7689/align-agent-bot-ownership-with-unassigned-counts-and-pagination

## Follow-ups

-
https://linear.app/chatwoot/issue/CW-7870/refresh-agentbot-ownership-state-when-deleting-an-agent-bot
tracks ownership refresh during AgentBot deletion.
-
https://linear.app/chatwoot/issue/CW-7899/refresh-saved-filter-totals-after-live-conversation-ownership-changes
tracks the existing saved-filter header count refresh gap.

## Why

The backend treated every conversation without a human assignee as
unassigned, even when an AgentBot owned it. The frontend already hid
AgentBot-owned conversations from the Unassigned list, so counts,
pagination, filters, unread membership, direct-access permissions, and
auto-assignment could disagree with the visible queue.

## What changed

- Treat conversations with either a human assignee or AgentBot owner as
assigned.
- Keep conversation counts, pagination, unread memberships, advanced
filters, and automation assignee conditions aligned with the shared
ownership semantics.
- Keep human assignee equality and not-equality filters human-only, even
when a human and AgentBot have the same numeric ID.
- Exclude AgentBot-owned conversations from both legacy and V2 human
auto-assignment, and from unassigned-only Enterprise access.
- Preserve AgentBot ownership when Twilio or WhatsApp call flows reuse
or accept an assigned conversation.
- Emit ownership-change updates when only the AgentBot owner changes, so
connected clients refresh queue state.

## Validation

- AgentBot assignment changed ownership to the bot, moved the
conversation to pending, and removed it from the open queue.
- Assignee "is present" returned human- and AgentBot-owned
conversations; "is not present" returned only genuinely unassigned
conversations.
- Automation assignee presence conditions treated AgentBot ownership as
present and did not execute the absent-owner path.
- Live human-assignee equality and not-equality filters excluded
AgentBot-owned conversations, including numeric ID collisions.
- A 32-conversation pending queue loaded across pagination with matching
totals and no missing or duplicate rows.
- AgentBot ownership changes and human takeover updated filtered rows
immediately without a reload.
- Human takeover opened the conversation and restored the public reply
composer; subsequent unassignment kept the conversation open.
- An unassigned-only custom-role agent saw only genuinely unassigned
conversations and could not see AgentBot-owned conversations.
- AgentBot-owned conversations showed the handled-by-bot banner, Take
over action, and disabled public reply composer.
- New conversations in the connected inbox were assigned to the AgentBot
and excluded from human auto-assignment.
- Opening an AgentBot-owned conversation did not let the legacy
assignment callback or its locked recheck replace the bot.
- Moving an AgentBot-owned conversation to an auto-assigning team
preserved the bot and did not create a second human owner.
- Twilio conference pickup, Twilio outbound reuse, WhatsApp outbound
reuse, and inbound WhatsApp acceptance preserved existing AgentBot
owners.
- Focused ownership, filters, pagination, permissions, unread-count,
auto-assignment, frontend, and lint checks passed locally.
- GitHub Actions, Docker builds, CircleCI, security checks, and the
final Codex review are green on the final head.

spec/models/concerns/assignment_handler_shared.rb

@@ -50,6 +50,17 @@ shared_examples_for 'assignment_handler' do
                                 content: "Assigned to #{conversation.assignee.name} via #{team.name} by #{agent.name}" }))
       end
 
+      it 'keeps AgentBot ownership when assigning an auto-assigning team' do
+        team.update!(allow_auto_assign: true)
+        agent_bot = create(:agent_bot, account: conversation.account)
+        conversation.update!(assignee: nil, assignee_agent_bot: agent_bot)
+
+        conversation.update!(team: team)
+
+        expect(conversation.reload.assigned_entity).to eq(agent_bot)
+        expect(conversation.assignee).to be_nil
+      end
+
       it 'wont change assignee if he is already a team member' do
         team.update!(allow_auto_assign: true)
         assignee = create(:user, account: conversation.account, role: :agent)