Agent rename: relay profile sync failure is silently swallowed with no user feedback

[cameronhotchkies]

Summary

When a user renames an agent via the "Agent name" field in the agent settings dialog, the UI always closes as if the save succeeded — even when the relay-side kind:0 profile republish fails. The user has no way to know the relay still has the old name.

Root Cause

update_managed_agent in agent_models.rs performs two phases:

1. Local save (disk write + AGENTS.md regeneration) — always synchronous, always succeeds
2. Relay profile sync — async HTTP POST publishing a new kind:0 event with display_name = new_name. This can fail (network blip, auth expiry, relay unreachable).

The Tauri command returns a profile_sync_error: Option<String> field. In the frontend, useUpdateManagedAgentMutation's onSuccess handler receives the result, but:

// desktop/src/features/agents/ui/AgentInstanceEditDialog.tsx:596-598
if (result.profileSyncError) {
  console.warn("Relay profile sync failed:", result.profileSyncError);
}
handleOpenChange(false);  // dialog closes regardless

The error is console.warn'd only. The dialog closes, showing success. No toast, no inline error, no retry prompt.

Impact

If the relay sync fails:

• The relay retains the old kind:0 (display_name = "Varys")
• The CLI mention resolver (resolve_content_mentions) fetches kind:0 fresh at send time — so @Osmosmith resolves to nothing
• The ACP prompt builder fetches kind:0 fresh at each turn — other agents see the old name in the From: line
• The Postgres users.display_name is only updated via the kind:0 side-effect handler, so user search also returns stale results
• There is no automatic retry for sync_managed_agent_profile — unlike kind:30177 which has a flush_pending_events loop with retry semantics

The local record and AGENTS.md are updated correctly in all cases.

Affected Code

• desktop/src-tauri/src/commands/agent_models.rs:956-976 — relay sync, error goes to profile_sync_error
• desktop/src/features/agents/ui/AgentInstanceEditDialog.tsx:596-598 — error silently logged, dialog closed

Suggested Fix

Surface profileSyncError as a visible warning in the dialog — a toast or inline banner stating the local save succeeded but the relay profile may be out of date, with a prompt to retry or restart the agent. Do not block the save; the local rename is valid and should persist.

Alternatively, add retry-with-backoff semantics to sync_managed_agent_profile mirroring the flush_pending_events loop that already handles kind:30177/30175 republishes.

Discovered via

Investigation of #1743 (agent identity rename not propagating to relay after UI save).