refactor(agent): align 'Agent' naming to 'AI/LLM' to match current implementation

- locales/en.json: 'Enrich Metadata (Agent)' -> 'Enrich Metadata (AI)'
- Rename SKILL.md -> prompt.md with backward compat in skill_registry.py
- JS context menu action IDs: enrich-hf-agent -> enrich-hf-llm
- HTML template data-action attributes synced to match
- docstring cleanup: 'agent skill' -> 'skill pipeline' / 'feature'

static/js/components/ContextMenu/BulkContextMenu.js

@@ -274,7 +274,7 @@ export class BulkContextMenu extends BaseContextMenu {
             case 'resume-metadata-refresh':
                 bulkManager.setSkipMetadataRefresh(false);
                 break;
-            case 'enrich-hf-agent-bulk':
+            case 'enrich-hf-llm-bulk':
                 this.enrichBulkWithAgent();
                 break;
             case 'delete-all':

static/js/components/ContextMenu/LoraContextMenu.js

@@ -63,7 +63,7 @@ export class LoraContextMenu extends BaseContextMenu {
             case 'refresh-metadata':
                 getModelApiClient().refreshSingleModelMetadata(this.currentCard.dataset.filepath);
                 break;
-            case 'enrich-hf-agent':
+            case 'enrich-hf-llm':
                 this.enrichWithAgent(this.currentCard.dataset.filepath);
                 break;
             case 'exclude':