Completed Experiments Evaluate Enabled

Completed experiments now evaluate as permanently enabled

Features gated behind a completed experiment were treated as disabled instead of permanently enabled, so functionality that graduated out of experiment status could silently stop working.

The one affected code path was hcl validate --inputs with a git filter expression such as --filter '[HEAD~1...HEAD]': after the filter-flag experiment completed, the command stopped preparing git worktrees for the filter. Git filter expressions now work with hcl validate --inputs again, matching find, list, and the other commands that accept filters.