docs: improve test suite documentation

[man4ish]

Summary

Documentation-only pass over the Studio Python test suite, following the standard used in the completed API Gateway / Workbench campaigns.

• All 30 Studio-owned test modules now have module docstrings with the Developer: attribution block (30/30)
• All 70 Test* classes are documented (70/70)
• All 394 test_* functions have assertion-specific docstrings (394/394)
• Selective fixture/helper docs where they encode isolation, topology or credential-gating assumptions
• Existing strong docstrings preserved; one stale docstring corrected (see below)

Only docstrings changed: 30 test files, +794 / -6. No production code, compose files, Redis/ACL config, or dependencies touched.

Verification

• AST equivalence vs b7dd2a3: executable AST differences = 0 across all 30 files
• Line-level: all 794 added lines fall inside docstrings; the 6 removed lines are the corrected docstring
• Syntax: 0 failures; git diff --check clean
• Collection: --collect-only identical before/after (463 ids for the whole suite)
• Tests (bounded, same set pre and post): focused 87 passed; broad 265 passed / 1 failed. Identical before and after.

Excluded from execution (documented only): tests/integration/ (needs the live stack, creates users) and docker-socket-proxy/tests/test_proxy_live_integration.py (drives the host Docker daemon).

Docstring corrections

test_redis_aof_config_is_identical_across_all_profiles cited a test that does not exist and described two files when it compares three profiles; it now states its actual contract. Two recovery-drill docstrings were reworded to say they check script text rather than runtime behavior.

Known issues, not addressed here (need separate disposition)

1. Pre-existing failing test tests/test_compose_network_exposure.py::test_redis_aof_config_is_identical_across_all_profiles fails on main (b7dd2a3): docker-compose.yml runs redis with --aclfile /data/users.acl, but docker-compose.release.yml and docker-compose-release.yml do not. Either the test is stale or the release profiles have a Redis ACL configuration gap. This PR does not change that behavior.
2. Live proxy test skip gate: test_proxy_live_integration.py is described as opt-in, but it only skips when no docker CLI/socket exists, so a plain pytest on a Docker host will run real docker run/exec/rm -f.

🤖 Generated with Claude Code