Harden NPC profile UI loading

[RANGROO]

Summary

• Reject stale or deleted NPC profile modal requests with an explicit 404 response instead of rendering an empty editor.
• Validate modal responses against the requested NPC ID and show a recoverable loading/error state.
• Reset modal editing to the General tab when switching NPCs.
• Ignore aborted or stale list refreshes and retain the current list when a refresh fails.

Problem

The NPC Profiles UI treated any iframe or list response as successful. A stale profile ID, incomplete response, overlapping request, or failed AJAX refresh could therefore appear as an empty or randomly unloaded profile with no visible explanation.

Validation

• php -l ui/core/npc_master.php
• git diff --check
• Live browser: loaded two different NPC profiles and verified the requested names/IDs, General-tab reset, and page-2 AJAX pagination with 12 cards and no browser warnings.
• Runtime probes: 20/20 valid modal requests returned the expected profile marker; 10/10 missing IDs returned a marked HTTP 404; 20/20 list requests returned complete pagination and card grids.
• Runtime Apache log showed no new PHP warnings/errors.
• Deployed the changed file locally to /var/www/html/HerikaServer and verified the deployed checksum and www-data:www-data ownership.

Review notes

This narrowly changes ui/core/npc_master.php, which also overlaps open PRs #594 and #634. No database migration, generated binary, or new test file is included.