feat: add emergency-stop bridge rehearsal

[Jdelg718]

Summary

• Adds Phase 15 dry-run-only bridge rehearsal.
• Proves emergency stop exits before durable ledger claim.
• Logs dry-run rehearsal as dry_run_logged without provider execution.
• Skips duplicate audit_id replay through the Phase 14 ledger.
• Records Kent's selected Phase 16 target: Microsoft Outlook warning draft sandbox contract.

Safety Boundaries

• No OAuth implementation.
• No provider credentials.
• No Gmail/Microsoft/IMAP/SMTP/n8n/provider calls.
• No live provider mutation nodes.
• No send-reply mutation.
• Provider execution remains not_performed.

Verification

• python3 scripts/validate_n8n_workflow_exports.py
• python3 -m py_compile outreach_filter.py botfucker/*.py scripts/validate_n8n_workflow_exports.py
• python3 -m unittest discover -s tests -v