fix(#992): optimize rt-without-atoms XSL with xsl:key

[ImilB]

Closes #992.
Problem

The rt-without-atoms XSL transformation exceeds 100ms threshold on large XMIR files (~128-129ms).
Root Cause

The check not(//o[eo:atom(.)]) scans the entire document when no atom is found.
eo:atom(.) = exists($o/o[@name=$eo:lambda]) performs a child lookup per element.
When the XMIR file has no atoms, every element is visited, making the cost O(n × degree).
Solution

Added xsl:key for fast lookup of atoms.

[ImilB]

@volodya-lombrozo Here is the proof that the optimization works:

Local XSLT performance test

Test environment:

• Saxon HE 12.10
• Java 17.0.19
• Windows 11

Result:

[ImilB]

@yegor256 solved #992

[volodya-lombrozo]

/benchmark

[github-actions]

⚠️ The /benchmark run failed. See the failed workflow run for details.

[volodya-lombrozo]

@ImilB Could you rebase your changes on master, please? I will be able to run benchmarks on you changes then.

[volodya-lombrozo]

@ImilB Can we use eo:atom function here?

[ImilB]

Yes, absolutely. Thanks for pointing that out. I replaced xsl:key with eo:atom(.) here and rebased the branch on master.

[volodya-lombrozo]

Thanks for the contribution! Unfortunately I can't merge this as-is - none of the 4 commits are signed, and our release tooling (Rultor) rejects unsigned commits regardless of CI status. Could you sign your commits and reopen? Here's GitHub's guide on setting that up: https://docs.github.com/en/authentication/managing-commit-signature-verification/signing-commits

[ImilB]

@volodya-lombrozo I added commit signing, recreated the branch with a signed commit, and reopened the PR. GitHub now shows the commit as Verified.

[0crat]

@volodya-lombrozo Thanks for the review! You've earned +4 points for this: +12 as a basis; -5 for very few (1) comments; -4 for too few (6) hits-of-code; +1 to give you at least something. Your running score is +456; don't forget to check your Zerocracy account too).