fix(#95): replace regex JSON extraction with outermost-brace approach

_parse_action() used r'\{[^{}]*\}' regex which fails on nested
JSON (e.g. oracle text with braces). Now uses text.find/rfind to
extract the outermost { } block, handling nested structures.
Fixes issue #95 item 2.

src/commander_ai_lab/sim/deepseek_brain.py

@@ -653,9 +653,10 @@ class DeepSeekBrain:
         text = re.sub(r'\s*```$', '', text)
         text = text.strip()
 
-        json_match = re.search(r'\{[^{}]*\}', text, re.DOTALL)
-        if json_match:
-            text = json_match.group(0)
+        start = text.find('{')
+    end = text.rfind('}')
+    if start != -1 and end != -1 and end > start:
+        text = text[start:end + 1]
 
         try:
             parsed = json.loads(text)