Bump LeanEval to Lean v4.34.0

[kim-em]

Bump the benchmark and evaluation toolchain to Lean v4.34.0.

• pin Lean v4.34.0 and the matching Mathlib release commit
• align lean4-cli with Mathlib v4.34.0
• pin the matching v4.34.0 lean4export and comparator releases
• migrate the affected catalogue modules to their Mathlib v4.34.0 APIs and imports
• update the dependency ledger and local setup instructions

Submission-side evaluator update (merged): leanprover/lean-eval-submissions#1737

Local verification completed:

• full lake build (8,947 jobs)
• strict warning-clean builds of all seven migrated catalogue modules
• Lean tests (171 assertions) and Python tests (35)
• action pin audit
• lake_env_probe, sandbox-engaged probe, environment-allowlist probe, and both artifact-tamper probe phases
• v4.34.0 lean4export and comparator builds
• generated two_plus_two end-to-end comparator smoke: Mathlib build, nanoda acceptance, and Lean kernel acceptance
• backward-compatibility smoke against the current v4.33 workspace with the v4.34 evaluator stack