chore: improve typing and consolidate utilities

- add type annotations across utility modules  
- refactor printer system, agent utils, and imports for consistency  
- remove unused modules, constants, and redundant patterns  
- improve runtime type checks, exception handling, and guardrail validation  
- standardize warning suppression and logging utilities  
- fix llm typing, threading/typing edge cases, and test behavior

src/crewai/utilities/constants.py

@@ -1,19 +1,32 @@
-TRAINING_DATA_FILE = "training_data.pkl"
-TRAINED_AGENTS_DATA_FILE = "trained_agents_data.pkl"
-DEFAULT_SCORE_THRESHOLD = 0.35
-KNOWLEDGE_DIRECTORY = "knowledge"
-MAX_LLM_RETRY = 3
-MAX_FILE_NAME_LENGTH = 255
-EMITTER_COLOR = "bold_blue"
+from typing import Annotated, Final
+
+from crewai.utilities.printer import PrinterColor
+
+TRAINING_DATA_FILE: Final[str] = "training_data.pkl"
+TRAINED_AGENTS_DATA_FILE: Final[str] = "trained_agents_data.pkl"
+KNOWLEDGE_DIRECTORY: Final[str] = "knowledge"
+MAX_FILE_NAME_LENGTH: Final[int] = 255
+EMITTER_COLOR: Final[PrinterColor] = "bold_blue"
 
 
 class _NotSpecified:
-    def __repr__(self):
+    """Sentinel class to detect when no value has been explicitly provided.
+
+    Notes:
+        - TODO: Consider moving this class and NOT_SPECIFIED to types.py
+          as they are more type-related constructs than business constants.
+    """
+
+    def __repr__(self) -> str:
         return "NOT_SPECIFIED"
 
 
-# Sentinel value used to detect when no value has been explicitly provided.
-# Unlike `None`, which might be a valid value from the user, `NOT_SPECIFIED` allows
-# us to distinguish between "not passed at all" and "explicitly passed None" or "[]".
-NOT_SPECIFIED = _NotSpecified()
-CREWAI_BASE_URL = "https://app.crewai.com"
+NOT_SPECIFIED: Final[
+    Annotated[
+        _NotSpecified,
+        "Sentinel value used to detect when no value has been explicitly provided. "
+        "Unlike `None`, which might be a valid value from the user, `NOT_SPECIFIED` "
+        "allows us to distinguish between 'not passed at all' and 'explicitly passed None' or '[]'.",
+    ]
+] = _NotSpecified()
+CREWAI_BASE_URL: Final[str] = "https://app.crewai.com"