fix(secops): validate alert_id and return structured dict for alert tools

[dandye]

Summary

Addresses #265:

• Parameter Validation & Typing: Made alert_id: str a required first parameter on both get_security_alert_by_id and do_update_security_alert, and added validation to prevent passing None or empty strings to the Chronicle SDK.
• Structured Dict Return: Changed return types from escaped JSON strings (json.dumps(...)) to structured dictionaries (Dict[str, Any]), matching the actual SDK output format and downstream client/test expectations.
• Error Handling: Log exceptions with logger.error(..., exc_info=True) and return structured error dictionaries ({"error": ...}). Corrected copy-paste typo in do_update_security_alert exception message.
• Documentation: Updated docstrings to accurately document parameters, return types, and descriptions.

Fixes #265

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Verification

• Hermetic Unit Tests: Added 8 unit test cases in tests/test_security_alerts_unit.py testing required parameter validation, structured dictionary return values, SDK call parameters, and error handling.
• Test Suite: Verified all 33 unit tests pass cleanly:

  uv run pytest tests/test_security_alerts_unit.py tests/test_secops_tools_unit.py tests/test_secops_parser_management_unit.py -v

• Linter & Formatting:

  uvx ruff check tests/test_security_alerts_unit.py
  uvx ruff format --check tests/test_security_alerts_unit.py