Harden Fugaku allocation and PR CI checks

[yoshifuminakamura]

Summary

• derive Fugaku/FugakuCN PJM group args from BK_ALLOCATION_PROJECT_ID and use the same scheduler_extra_args path in generated CI and test_submit.sh
• add warning-level shellcheck for changed app scripts so assignment/glob pitfalls such as SC2125 are caught on PRs
• add a repository-policy check that fails PR runs when the tested base SHA is stale
• document Fugaku manual-submit usage with BK_ALLOCATION_PROJECT_ID

Tests

• bash scripts/tests/test_scheduler_extra_args.sh
• bash -n scripts/job_functions.sh scripts/test_submit.sh scripts/tests/test_scheduler_extra_args.sh
• python3 -m py_compile scripts/tests/check_pr_base_current.py
• python3 scripts/tests/check_text_integrity.py
• git diff --check
• shellcheck -S error scripts/job_functions.sh scripts/test_submit.sh scripts/tests/test_scheduler_extra_args.sh
• BK_ALLOCATION_PROJECT_ID=ra000009 bash scripts/matrix_generate.sh code=qws system=Fugaku