fix: sync review — DEFAULTS logging.level "INFO" → "WARNING"

[A-NEW-001] Update ConfigResolver DEFAULTS to match spec change.
The doc repo updated the default logging level from INFO to WARNING
but the code was not updated.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: tercel

src/apcore_cli/config.py

@@ -18,7 +18,7 @@ class ConfigResolver:
 
     DEFAULTS: dict[str, Any] = {
         "extensions.root": "./extensions",
-        "logging.level": "INFO",
+        "logging.level": "WARNING",
         "sandbox.enabled": False,
         "cli.stdin_buffer_limit": 10_485_760,  # 10 MB
         "cli.auto_approve": False,