Update plugins for Goa v3.32.0

[raphael]

Update the plugins module and all three testing-example modules from Goa v3.31.1 to the published v3.32.0 release. Regeneration changes only 12 gen/goa.json version markers; plugin implementations, API designs, and generated Go code are unchanged.

The full preparation also updates gRPC from v1.83.2 to v1.84.0, refreshes Google RPC definitions and Smithy, and tidies module and workspace checksums. The final tidy adds the required indirect formatter dependency to the root module and updates the nested examples' indirect requirements.

All four modules retain their Go 1.26 minimum. CI now tests Go 1.26.8 and 1.27.1 explicitly with GOTOOLCHAIN=local. The root Makefile installs the Goa command selected by the module, runs generation, checks with Staticcheck, and invokes plugin tests, including the calculator, HTTP/gRPC, and JSON-RPC example modules. Their existing local plugin replacements remain intact so tests use this repository's implementation.

Validation on Go 1.27.1:

• The maintained make passed with Goa v3.32.0.
• go test ./mains ./testing passed. These existing generator suites are not invoked by the maintained plugin loop.
• Each module independently selects v3.32.0 with the published checksum and no Goa replacement.
• The complete preparation and release diff passes git diff --check.

Hosted checks on both CI toolchains remain pending. Review the four module files, generated version markers, and .github/workflows/ci.yml together.

This diff introduces no new designed requests, results, errors, or plugin APIs. No data migration or coordinated deployment is required. Consumers should update Goa and the plugins together, regenerate, and test their application. Rollback restores the prior modules and generated output together.