Reject open Hermes Tweet PR duplicates

[kriptoburak]

Summary

• Treat an existing open Hermes Tweet PR in the same target as a duplicate route.
• Add fixture coverage so future crawler hits with clean existing PRs stay rejected before new outreach.

Validation

• uv run --python 3.12 --extra dev pytest tests/test_submission_readiness.py
• uv run --python 3.12 --extra dev ruff format --check
• uv run --python 3.12 --extra dev ruff check
• uv run --python 3.12 --extra dev python scripts/check_public_safety.py
• uv run --python 3.12 --extra dev pytest tests/test_public_safety.py
• uv run --python 3.12 --extra dev pip-audit
• git diff --check

Note

Reject duplicate Hermes Tweet PRs when the same target already has an open PR

Adds guidance to SUBMISSION_READINESS.md stating that a new Hermes Tweet PR should not be opened if one already exists for the same target. Adds the corresponding phrase to safety_duplicates.txt so the duplicate check is enforced in tests.

^{Macroscope summarized 15371e6.}