use zero instead of literal 0.0

[tonyfettes]

In CI run:

https://github.com/moonbitlang/core/actions/runs/12911267303/job/36004981375

The CL compiler on Windows will raise a fatal error when there is division by literal 0.0, even if the literal is in type double.

This PR use named variables in double package to replace these usage.

[peter-jerry-ye-code-review]

‼️ This code review is generated by a bot. Please verify the content before trusting it.

⚠️ Potential Test Failures Due to Incorrect Expected Values

• Category: Correctness
• Code Snippet: In float/round_js.mbt, lines like inspect!((3.7 : Float).trunc(), content="3")
• Recommendation: Revert changes where float results (e.g., 3.0) are compared to integer strings ("3"), unless the language automatically truncates decimal zeros.
• Reasoning: If the actual result is a float (e.g., 3.0), expecting "3" without the decimal part may cause test failures. This change was not explained in the PR message and seems unrelated to the division-by-zero fix.

⚠️ Duplicated Variable Declaration Across Tests

• Category: Maintainability
• Code Snippet: Repeated let zero = 0.0 in multiple test blocks (e.g., double_to_int_test.mbt, double_to_int64_test.mbt)
• Recommendation: Consider defining a module-level constant or helper function to avoid redundancy.
• Reasoning: Redundant declarations increase maintenance overhead. If the initialization needs to change (e.g., to 0.0f), every test must be updated manually.

💡 Consider Descriptive Variable Name

• Category: Style Guide Compliance
• Code Snippet: let zero = 0.0 in test blocks
• Recommendation: Use a more descriptive name like divisor_zero to clarify intent.
• Reasoning: While zero is concise, divisor_zero explicitly indicates the variable's role in division, improving readability for future maintainers.

[coveralls]

Pull Request Test Coverage Report for Build 5053

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 85.186%

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Totals
Change from base Build 5046:	0.0%
Covered Lines:	5233
Relevant Lines:	6143

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💛 - Coveralls