refactor(rust): improve replace_all_placeholder

[shulaoda]

Summary

• To avoid incorrect matches, prevent matching [ext] as [extname].
• Ensure placeholders like [hash:] or [hash:o] are not matched.

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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[codspeed-hq]

CodSpeed Performance Report

Merging #9289 will not alter performance

_{Comparing shulaoda:refactor/improve-replace-all-placeholder (ddc37ee) with main (05524cd)}

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Summary

✅ 6 untouched benchmarks