`Number.prototype.toPrecision` returns wrong output for subnormal floats like `Number.MIN_VALUE`

[HiteshShonak]

Describe the bug
Number.prototype.toPrecision() returns wrong output for subnormal floats. instead of the correct significant digits, boa returns a bogus value with a wrong positive exponent.

To Reproduce

Number.MIN_VALUE.toPrecision(1)
// returns "0e+101" in Boa, expected "5e-324"

From repo root:

cargo run --bin boa -- -e 'console.log(Number.MIN_VALUE.toPrecision(1))'

Boa output:

0e+101

Node.js output:

node -e 'console.log(Number.MIN_VALUE.toPrecision(1))'
# 5e-324

Expected behavior
toPrecision() should return correctly rounded significant digits for all finite values including subnormals, matching Node.js and browser behavior.

Build environment:

• OS: Windows 11
• Version: 10.0.26200
• Target triple: x86_64-pc-windows-msvc
• Rustc version: rustc 1.94.0 (4a4ef493e 2026-03-02)

Additional context
Root cause is in core/engine/src/builtins/number/mod.rs - format!("{this_num:.100}") collapses subnormal values to all zeros, causing flt_str_to_exp to return a wrong positive exponent.

Spec reference: https://tc39.es/ecma262/#sec-number.prototype.toprecision

[HiteshShonak]

fix is ready, opening a pr shortly.