Docs: README and CLAUDE.md acknowledge the template experiment

[erikshafer]

Doc-only follow-up to #15. README.md and CLAUDE.md now acknowledge the template experiment; nothing in code, counts, or openspec/ moves.

README.md

• Intro and rule 1 ("the before twin is built earnestly") say the claim was tested on the Clean Architecture Solution Template (dotnet new ca-sln) and link the inventory section.
• New subsection under "The proof": where the experimental host lives, why its test project is separate (one process, one MediatR), the explicit dotnet test command, and that 6/10 is the template as shipped (content type, dropped errors dictionary).
• "Running it live" gets the template host's run command with its own database name.
• Repo tour lists experiments/before-clean-template/ and tests/LayerCake.ContractTests.CleanTemplate/, both marked outside the solution and the scorecard.

CLAUDE.md

• Experiments paragraph after the mode paragraph: outside the slnx, the scorecard, the version freeze, and the OpenSpec loop; folders and namespaces named after the artifact, never a person.
• Commands: the experiment's explicit command; root dotnet test excludes it.
• Talk-content rules: the experiment's line counts live in the inventory's final section and never join the twins' totals.
• Session workflow step 3: a change under experiments/ runs the CleanTemplate project and leaves the root suite untouched.
• Where detail lives: pointers to the inventory section and the 2026-09-06 build-log entry.
• Open items: the three calls from Experiment: slice 001 on the Clean Architecture Solution Template, counted against the twins #15 (6/10 vs the one-line problem+json fix; 17 vs 13 touched; a second template variant).

Verification

dotnet build 0 warnings; root dotnet test 54/54 contract + 15/15 unit, unchanged. All three edited files stay CRLF.