Detect and wrap missing Jinja expressions

[zhongkaifu]

Motivation

• Some params contain Jinja-like variable expressions but are missing the surrounding {{ }} markers and should be auto-wrapped to become valid templates.
• The change aims to detect those unwrapped variable-like strings and normalize them into proper Jinja template strings before validation/execution.

Description

• Add POTENTIAL_JINJA_EXPR regex and helper looks_like_missing_jinja to identify variable-like text that appears to reference fields.
• Add has_unwrapped_variable which uses the configured Jinja environment (get_jinja_env) to more strictly detect unwrapped expressions that can be parsed as Jinja expressions.
• Modify _normalize_jinja_expr to call has_unwrapped_variable and automatically return a wrapped template like "{{ ... }}" when appropriate.
• Add test_missing_jinja_expression_is_wrapped to tests/test_jinja_validation.py to cover the auto-wrapping behavior.

Testing

• Ran python -m pytest tests/test_jinja_validation.py which executed the file's test suite.
• All tests in that file passed (4 passed).

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Codex Task