fix: remove global shared state from observability hooks

- Remove _global_hooks, enable_observability(), disable_observability(), and get_hooks()
- Observability is now strictly per-agent/per-pipeline to comply with AGENTS.md Rule 4.5
- Agent class already correctly uses per-instance ObservabilityHooks() when observe=True
- Eliminates shared mutable state between agents for multi-agent safety

Addresses critical architecture gap identified in PR #1277 final review.

Co-authored-by: Mervin Praison <MervinPraison@users.noreply.github.com>

Author: MervinPraison

src/praisonai-agents/praisonaiagents/escalation/observability.py

@@ -8,7 +8,6 @@
 import logging
 from praisonaiagents._logging import get_logger
 import time
-import threading
 from dataclasses import dataclass, field
 from typing import Any, Dict, List, Optional, Callable
 from enum import Enum
@@ -292,24 +291,6 @@ def get_summary(self) -> Dict[str, Any]:
             "final_stage": self._current_stage.name if self._current_stage else None,
         }
 
-# Global hooks instance (opt-in) - protected by lock
-_global_hooks: Optional[ObservabilityHooks] = None
-_hooks_lock = threading.Lock()
-
-def get_hooks() -> Optional[ObservabilityHooks]:
-    """Get global observability hooks."""
-    return _global_hooks
-
-def enable_observability() -> ObservabilityHooks:
-    """Enable global observability."""
-    global _global_hooks
-    with _hooks_lock:
-        if _global_hooks is None:
-            _global_hooks = ObservabilityHooks(enabled=True)
-        return _global_hooks
-
-def disable_observability():
-    """Disable global observability."""
-    global _global_hooks
-    with _hooks_lock:
-        _global_hooks = None
+# NOTE: Observability is now per-agent/per-pipeline to comply with multi-agent safety.
+# Each agent creates its own ObservabilityHooks instance when observe=True.
+# See agent.py:2236 for the correct per-instance pattern.