pipeline v4.1.8

Fixed:
- python-bench / python-lib pytest: uv venv now uses --clear so a
  cached .venv/ from the cache key uv-$CI_COMMIT_REF_SLUG doesn't
  block a fresh re-run. Surfaced by sysml-bench's MR pipeline rerun
  after the v4.1.7 bump.
- grammar-rust tree-sitter-cli install path: pin --root /usr/local
  so the installed binary lands at /usr/local/bin/tree-sitter which
  is universally on PATH. Previously cargo install succeeded but
  the binary went somewhere not on PATH, causing 'tree-sitter:
  command not found' at the next step. Surfaced by kebnf's MR
  pipeline (first time tree-sitter-validate ran end-to-end).

Lockstep bump v4.1.7 -> v4.1.8 across all template files.