Add Phase 0a black-box integration test suite

81 tests across 11 files plus a 5-module harness (load, pg, streams,
containers, payloads), covering all eleven Phase 0 goals and all 13 named
chaos-flag pathologies. Talks to the system only over HTTP, Postgres, Redis,
and the Docker CLI -- no imports of application code. RED-BASELINE.md records
the suite failing red against the empty repo before any implementation
existed; README.md documents the request-contract fields invented to fill
gaps in the spec, measurement methodology, and known-flaky tests.

This suite is a frozen contract from this point forward per CLAUDE.md.

requirements-test.txt

@@ -0,0 +1,6 @@
+pytest>=8.0,<9
+pytest-asyncio>=0.23,<1
+pytest-timeout>=2.3,<3
+httpx>=0.27,<1
+psycopg[binary]>=3.1,<4
+redis>=5.0,<6