Fix count-min sketches test snapshots should use binary mode

[tisonkun]

... otherwise \n would be \r\n on Windows and cause apache/datasketches-rust#92 to fail.

[tisonkun]

Seems other snapshot generations already use binary mode.

[Copilot]

Pull request overview

This PR ensures Count-Min sketch test snapshot files are written in binary mode so serialized output is consistent across platforms (notably avoiding CRLF translation on Windows).

Changes:

• Open snapshot std::ofstream streams with std::ios::binary for the empty and non-empty serialization tests.

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[PsiACE]

since it looks like all the other files end with ".sk" , only count min with .bin

[coveralls]

Coverage Report for CI Build 28152728714

Coverage remained the same at 82.199%

Details

• Coverage remained the same as the base build.
• Patch coverage: No coverable lines changed in this PR.
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	21476
Covered Lines:	17653
Line Coverage:	82.2%
Coverage Strength:	1354329.76 hits per line

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💛 - Coveralls

[tisonkun]

since it looks like all the other files end with ".sk" , only count min with .bin

Good point. As other impls may also depend on the name, I'd sync with @leerho @proost @freakyzoidberg first to make the unify if any.

[proost]

Thank you! I agree with changing file extension to ".sk".

[tisonkun]

Thank you! I agree with changing file extension to ".sk".

I agree with this. I can update it in this PR or do it in a follow-up.

One possible impact is that datasketches-java and datasketches-go, IIRC, test against these snapshot files. So they may be affected by the name changes as well. But for sure we can update there cascadingly, just need to inform all the related devs.

[tisonkun]

Pushed 7c993ed for the rename.

I'm going to merge this patch later today or tomorrow and fix any impact downstream.