docs: define a seam as the (Service, Service provider, Consumer) trio

docs/subsystems/sandbox.md

@@ -155,9 +155,9 @@ Provider selection, probing, caching, and backend-specific enforcement reports b
 
 Generated from source by `scripts/gen-cordis-catalog.ts` (verified fresh by `pnpm run verify-cordis-catalog` in doc-sync; regenerate with `pnpm run gen-cordis-catalog`) — this section is byte-identical in both language sides of the page. Signature blocks use a `ts cordis-catalog` fence and keep the original source JSDoc; dispatch modes are defined in the [primer](../cordis-primer.md#dispatch-modes), and the framework-inherited `ctx` surface lives in [cordis-api/inherited.md](../cordis-api/inherited.md).
 
-<a id="ctxsandbox--sandboxprovider-abstract-seam"></a>
+<a id="ctxsandbox--sandboxprovider"></a>
 
-### `ctx.sandbox` — `SandboxProvider` (abstract seam)
+### `ctx.sandbox` — `SandboxProvider`
 
 Abstract process-sandbox service. confine must return enforcing argv or fail closed at wrap or runner-execution time; silent unconfined passthrough is forbidden. Functional probes arbitrate multi-runner chains and may be skipped for a sole candidate, whose own refusal remains the fail-closed end.