refactor(semantics): migrate legacy @TIER to @COMPLEXITY annotations

- Replaced @TIER: TRIVIAL with @COMPLEXITY: 1
- Replaced @TIER: STANDARD with @COMPLEXITY: 3
- Replaced @TIER: CRITICAL with @COMPLEXITY: 5
- Manually elevated specific critical/complex components to levels 2 and 4
- Ignored legacy, specs, and node_modules directories
- Updated generated semantic map

frontend/src/lib/api/assistant.js

@@ -1,5 +1,5 @@
 // [DEF:frontend.src.lib.api.assistant:Module]
-// @TIER: STANDARD
+// @COMPLEXITY: 3
 // @SEMANTICS: assistant, api, client, chat, confirmation
 // @PURPOSE: API client wrapper for assistant chat, confirmation actions, and history retrieval.
 // @LAYER: Infra-API