signal_contract_audit --ci does not check that docs/signal_contracts.md matches render() #3341

Problem

docs/signal_contracts.md says it is "Rendered from gitgalaxy/standards/signal_contracts.py … Do not edit by hand", but nothing checks that it's in sync. tests/signal_contract_audit.py --ci checks the registry against the module, not the rendered file against render().

It had drifted on main. Re-rendering for #3337 also added three entries other merged PRs had left out:

• the calls_out contract row (Epic: Refactor calls_out_to extraction to support non-C language paradigms #3264);
• _calls_out_ignore (calls_out Phase 3 Batch 0: foundation — per-language ignore mechanism + family paradigm constants #3282);
• _line_gates (perf: per-line gating for the line-anchored rules the literal prefilter can't touch #3072).

Fix

In --ci mode, fail when RENDER_PATH.read_text() != render(), with the message "run python tests/signal_contract_audit.py --render". The signal-contract CI job then catches the next drift in the PR that causes it.

Found during epic #3313, step 4 (#3337).