Rule: no tests, no PR

Scope: any ticket that touches source code (the code-ticket workflow).

A project with no tests gives a code change nothing to stand on. Therefore:

• Before implementing a code ticket, you MUST run the deterministic gate: python3 scripts/run_tests.py --check.
• If it exits non-zero (no test runner detected), you MUST NOT implement the change and MUST NOT open a PR. Write tests first, then re-run the gate.
• You MUST NOT rationalise around this ("it's a tiny change", "I'll add tests later"). No tests means no PR, full stop.

The check is mechanical and lives in scripts/run_tests.py (--check); this rule is the obligation to honour its exit code.