`anonymous-formation` XSL transformation is too slow on large XMIR files

I'm getting performance warnings when running lints against eo-runtime:

[WARNING] XSL transformation 'anonymous-formation' took 125ms, whereas threshold is 100ms

What happens: The template uses a nested descendant scan:

<xsl:for-each select="//o[not(@name) and not(@base) and ...]">
  <xsl:for-each select=".//o[starts-with(@base, 'ξ.ρ.') and not(eo:matches-any-void(@base, $allowed))]">

For each anonymous formation in the outer loop, the inner loop searches all its descendants again. This is an O(n²) pattern. Additionally, eo:matches-any-void calls matches() for every allowed-void pattern on each inner element.

What should happen: The transformation completes within the 100ms threshold. Restructuring to a single-pass approach or using xsl:key to pre-index the relevant @base values would remove the quadratic cost.