* chore: enforce test directory conventions
Move package, app, and tool tests out of src and add guard enforcement so source directories stay source-only.
* ci: use guard and package-scoped tests
Run the new repository guard in CI and keep test execution aligned with package-scoped commands after removing root aliases.
* ci: align stable release guard check
Use the new repository guard in stable release verification after replacing the residual-JS-only script.
* chore: tighten test layout enforcement
Enforce sibling tests directories, typecheck moved test suites with dedicated configs, and refresh remaining guidance that pointed at src-based tests.
* chore: clarify no-emit test tsconfigs
Explicitly disable declaration-only emit in test tsconfigs so review tooling sees they are no-emit typecheck configs.
