feat(query): ignore system attributes _id/_time/_version when matching

[SAY-5]

Closes #460. The except call in if_absent and just_one used string keys while attrs is keyed by symbols, so the system attributes were never stripped from the match query. This passes symbols to except and adds regression tests for both helpers.

[0crat]

@SAY-5 Hi there! Your branch name "fix/except-symbol-keys" doesn't follow our naming convention, so I've deducted -6 points as per our team policy. Please use the ticket number as the branch name next time - in this case, "465" would be perfect. Your current score is -6, and you can check your Zerocracy account for updates.

[edmoffo]

Diff matches the analysis in #460: attrs carries symbol keys throughout, so passing symbols to except removes the system attributes that the docstrings already promised would be skipped. Regression tests cover both if_absent and just_one, and CI is green.

[bibonix]

The change in both if_absent.rb and just_one.rb passes symbol keys (:_id, :_time, :_version) to Hash#except instead of strings, which matches the symbol-keyed attrs hash and actually strips the system attributes from the match query as the docstrings already promised. The two regression tests cover both helpers and both end up at the right place: if_absent returns nil when only the system attribute differs, and just_one returns the existing fact. CI is green.

[0crat]

@bibonix Hey! Nice work on that review 👍 You snagged +10 points this time: started with the base +18 but lost -8 since no comments were posted during the review. Just so you know, you could've maxed out at +24 points if there were more comments and hits-of-code involved - something to keep in mind for next time! Your running score is now +400, so don't forget to check your Zerocracy account too.

[0crat]

@edmoffo Great work on the review! 🎉 You've earned +10 points (+18 base, -8 for missing comments). Your current score is +70 - keep building momentum! Check your Zerocracy account for more details.