fix: Run response decorators inside interceptor ScopedValue scope

[thced]

Summary

• Move the response-decorator loop into the base case of DispatchHandler.invoke(...) so decorators execute inside every RequestInterceptor's ScopedValue scope. Honors the contract documented in README "Combining the two" — previously a decorator that called CORRELATION_ID.get() threw NoSuchElementException because the interceptor's scope had already unwound.
• Interceptors now observe the decorated Response on the way back up the stack (a tracing interceptor wrapping next.proceed() sees the final status, headers, and body).
• A decorator exception now propagates through the interceptor chain — interceptors that try/catch around next.proceed() will observe decorator failures. Documented in README.

Changes

• DispatchHandler.handle/invoke refactor (one method-pair, ~7 lines).
• ResponseDecorator javadoc cross-references RequestInterceptor + ScopedValue visibility.
• README "Combining the two" notes the decorator-exception propagation behavior.
• Three new unit tests in DispatchHandlerTest + one IT in DecoratorAndInterceptorIT.

Spec: docs/superpowers/specs/2026-05-23-decorator-scoped-value-scope-design.md
Plan: docs/superpowers/plans/2026-05-23-decorator-scoped-value-scope.md

Test plan

• Unit: decorator reads interceptor-bound ScopedValue and stamps a header
• Unit: interceptor's next.proceed() returns the decorator-modified Response
• Unit: interceptor try/catch around next.proceed() catches a throwing decorator; final response carries the catch-block status
• IT: end-to-end through OpenApiServer — decorator reads TENANT bound by interceptor, stamps X-Tenant-Id
• mvn verify passes (475 unit + 68 IT, 0 failures)
• JaCoCo: 100% instruction + branch coverage on DispatchHandler

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

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