test(BA-7802): add the shared components the system concern scenarios use

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📚 Stacked PRs

Part of the system concern scenario stack (BA-7802). Merge in order (bottom-up):

1. 👉 test(BA-7802): add the shared components the system concern scenarios use #14510 — test(BA-7802): shared components the system concern scenarios use ← you are here
2. test(BA-7802): add scenario tests for the runtime variant adapter #14521 — test(BA-7802): runtime variant
3. test(BA-7802): add scenario tests for the runtime variant preset adapter #14522 — test(BA-7802): runtime variant preset
4. test(BA-7802): add scenario tests for the resource slot type calls #14523 — test(BA-7802): resource slot type
5. test(BA-7802): add scenario tests for the retention policy adapter #14524 — test(BA-7802): retention policy
6. test(BA-7802): add scenario tests for the login client type adapter #14525 — test(BA-7802): login client type
7. test(BA-7802): add scenario tests for the client IP masking adapter #14526 — test(BA-7802): client IP masking
8. test(BA-7802): add scenario tests for the secret adapter #14527 — test(BA-7802): secret

Fork at #14510: #14521 → #14522 is ordered; #14523–#14527 each sit on #14510 alone and may merge in any order after it.

Part of BA-7802

Summary

• Add tests/scenario/bai_scenario/components/system.py, the one piece every system-concern scenario table shares: a caller of a given role and nothing else (SomeoneAlone, lay_a_caller), the enforcement switch the entity gate reads (ENFORCEMENT), and the marker an edit uses for a place it must leave as laid (KEPT).
• A system entity is created in no scope, so its tables lay no place — only the caller and the rows the call reads. That is why this is all the stack shares; each entity PR above brings its own seed, components, KNOWLEDGE.md, tests and report.md.

Beside the stack, #14528 fills service_catalog/KNOWLEDGE.md alone: no write spec lays a catalog row (the registration event handler inserts it directly), so it has no tests yet and sits on main by itself.

The twelve global wirings of the concern (EtcdConfigProcessors, ManagerAdminProcessors) have no adapter package and therefore no KNOWLEDGE.md slot; they are out of this stack.

Test plan

• pants check lint on the new module
• CI

🤖 Generated with Claude Code

https://claude.ai/code/session_01Snp9H2jEVbB2s1C6ixUHGn

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Superseded: the stack was dissolved into independent PRs, one issue each — #14535 (BA-7843 runtime variant), #14536 (BA-7844 preset), #14538 (BA-7845 resource slot type), #14542 (BA-7846 retention policy), #14543 (BA-7847 login client type), #14544 (BA-7848 client IP masking), #14545 (BA-7849 secret), #14546 (BA-7850 service catalog). Each carries components/system.py byte for byte; whichever merges first, the rest rebase clean.