Fix telemetry escaping reversibility

[orban]

Summary

• make hook telemetry TSV-safe by escaping backslashes, tabs, newlines, and carriage returns before writing
• decode escaped telemetry only at dashboard display time so literal backslash sequences remain visible to operators
• add regression coverage for literal escape sequences and control-character round trips, and document the logging contract

Testing

• bash tests/test_telemetry.sh
• bash tests/test_hooks.sh
• bash tests/test_feedback_loop.sh
• bash tests/test_stop_hook.sh
• python -m pytest eval-harness/tests/test_task_runner.py