Fix JSON decoder bug with small floats like 0.0000040357127006276845

[Copilot]

The JsonDecoder was incorrectly handling small floats with exactly 24 characters due to a typo in the readNum() method. When parsing numbers character by character, the decoder was missing c23 and duplicating c24 in the fromCharCode call, causing precision loss.

Problem:

const decoder = new JsonDecoder();
const smallFloat = 0.0000040357127006276845;
const decoded = decoder.decode(Buffer.from(JSON.stringify(smallFloat), 'utf-8'));

console.log(smallFloat);  // 0.0000040357127006276845
console.log(decoded);     // 0.000004035712700627685 (incorrect - lost precision)

Root Cause:
In JsonDecoder.ts line 587, the fromCharCode call was missing c23:

// Before (incorrect)
const num = +fromCharCode(c1, c2, ..., c22, c24);  // missing c23!

// After (fixed)  
const num = +fromCharCode(c1, c2, ..., c22, c23, c24);

Fix:

• Corrected the typo to include both c23 and c24 in the proper order
• Added test case to prevent regression
• Verified all 2892 existing tests still pass

After the fix:

console.log(decoded);  // 0.0000040357127006276845 (correct!)

Fixes #46.

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[streamich]

LGTM

[github-actions]

🎉 This PR is included in version 1.9.1 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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