[Fix] Simplify GraphTokenizer smoke coverage

[baihchou8787]

Description

Simplifies GraphTokenizer tests to focused pass-through coverage and updates the paper-training protocol safeguards.

Changes

• Reduce GraphTokenizer, transformer, dataset, BPE, and paper-protocol tests to minimal import/load/forward paths.
• Update CI to run the simplified GraphTokenizer suite and remove the heavyweight official-GTE integration job.
• Add the paper-training GPU-idle option and guarantee at least one MLM target per eligible batch.
• Exclude local experiment outputs, caches, checkpoints, and logs from this PR.

Verification

• CI-equivalent checks in the CUDA GraphTokenizer environment: 55 passed, 2 skipped.
• GraphTokenizer suite: 16 passed.

Checklist

• The PR title starts with [Fix]
• Changes are complete
• All changes have test coverage
• Code is well-documented
• Examples affected by this change were updated
• Related issue is referred in this PR