El data studio: 10-loop improvement pass — full Engram DB explorer

Full-featured terminal explorer for the Engram knowledge graph built
natively in El. Features:
- ANSI-colored TUI with box-drawing borders and salience bars
- All API endpoints: stats, nodes by type/tier, search, edges,
  spreading activation, node detail with neighbor traversal
- Text report export via fs_write
- Offline/unreachable mode with helpful startup messages
- Interactive mode command reference
- ENGRAM_URL env var for connecting to non-default servers
- Uses json_get_raw for nested JSON object traversal

ql/test/llm_test.el

@@ -0,0 +1,10 @@
+// Test LLM native functions (with ANTHROPIC_API_KEY in env)
+let models: List = llm_models()
+println("Available models: " + int_to_str(list_len(models)))
+
+// This test skips actual API calls since they need env vars
+// Just verify the functions exist and don't crash on missing keys
+let missing_key_result: String = llm_call("claude", "ping")
+println("llm_call returned (may be error without API key): " + str_slice(missing_key_result, 0, 50))
+
+println("LLM function registration: OK")