fix(OMN-15918): harden deploy evidence probe

[jonahgabriel]

Summary

• buffer the GitHub contents response before the early-exit grep so bash -o pipefail cannot turn a valid match into SIGPIPE exit 141
• rerun the live source probe and rebind its receipt to the corrected contract entry

Verification

• uv run pytest tests/unit/scripts/test_lint_contract_check_values_corpus_baseline.py -q — 15 passed
• uv run validate-yaml contracts/OMN-15918.yaml — passed
• changed-file pre-commit hooks — passed
• exact buffered GitHub source probe — passed
• repository-wide pre-commit was also attempted; it reaches unrelated historical corpus failures already present on the parent branch, while all hooks scoped to these changed files pass

Dependency

Stacked onto the active OMN-15918 OCC companion branch so this correction can unblock onex_change_control#6396 and downstream omnibase_infra#2727.

Stacked-Parent: #6396

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