fix: apply installation branding replacement in tooltip copy (#13538)

## Summary
Fix hardcoded `Chatwoot` branding in two UI tooltips using the existing
`useBranding` flow so self-hosted/white-label deployments no longer show
the wrong brand text.

## Changes
- LabelSuggestion tooltip now uses:
  - `replaceInstallationName($t('LABEL_MGMT.SUGGESTIONS.POWERED_BY'))`
- Message avatar tooltip (native app/external echo) now uses:
  - `replaceInstallationName(t('CONVERSATION.NATIVE_APP_ADVISORY'))`

## Why
This follows the existing branding pattern already used in the product
and keeps behavior consistent across deployments.

## Notes
- No change to message logic or API behavior.
- `AGENTS.md` updated with a branding guidance note.

## Fixes
- Fixes https://github.com/chatwoot/chatwoot/issues/13306
- Fixes https://github.com/chatwoot/chatwoot/issues/13466

## Testing

<img width="195" height="155" alt="Screenshot 2026-02-13 at 3 55 39 PM"
src="https://github.com/user-attachments/assets/5b295cdd-6e5d-42c0-bbd7-23ba7052e1c3"
/>
<img width="721" height="152" alt="Screenshot 2026-02-13 at 3 55 48 PM"
src="https://github.com/user-attachments/assets/19cec2a0-451f-4fb3-bd61-7c2e591fc3c7"
/>

app/javascript/dashboard/components-next/message/Message.vue

@@ -43,6 +43,7 @@ import VoiceCallBubble from './bubbles/VoiceCall.vue';
 
 import MessageError from './MessageError.vue';
 import ContextMenu from 'dashboard/modules/conversations/components/MessageContextMenu.vue';
+import { useBranding } from 'shared/composables/useBranding';
 
 /**
  * @typedef {Object} Attachment
@@ -143,6 +144,7 @@ const { t } = useI18n();
 const route = useRoute();
 const inboxGetter = useMapGetter('inboxes/getInbox');
 const inbox = computed(() => inboxGetter.value(props.inboxId) || {});
+const { replaceInstallationName } = useBranding();
 
 /**
  * Computes the message variant based on props
@@ -472,7 +474,7 @@ const avatarInfo = computed(() => {
 
 const avatarTooltip = computed(() => {
   if (props.contentAttributes?.externalEcho) {
-    return t('CONVERSATION.NATIVE_APP_ADVISORY');
+    return replaceInstallationName(t('CONVERSATION.NATIVE_APP_ADVISORY'));
   }
   if (avatarInfo.value.name === '') return '';
   return `${t('CONVERSATION.SENT_BY')} ${avatarInfo.value.name}`;