fix(sdk): unbreak sdk-verify after the Go 1.27 bump

[aron-muon]

Summary

Go SDK / Verify generated Go SDK is red on main (7e52ab9). Two leftovers from the Go 1.27 bump in #6639.

1. The job installs the wrong Go. setup-go reads sdk/go/go.mod (go 1.26.0), but sdk-verify runs generator tooling out of the root module (cmd/help/openapi-normalize, cmd/help/ogen-client-wrapper), which is now go 1.27. setup-go pins GOTOOLCHAIN=local, so it fails outright rather than upgrading:

go: go.mod requires go >= 1.27 (running go 1.26.0; GOTOOLCHAIN=local)

Pointed setup-go at the root go.mod. Deliberately not bumping sdk/go/go.mod - that's the published floor for SDK consumers, and there's no reason to raise it just so CI can run root tooling. Building the 1.26-floor SDK module with a 1.27 toolchain is fine, and sdk-test/sdk-lint still pass.

2. The committed SDK artifacts are stale. The bump also edited a BuilderImage doc comment ("golang:1.26-alpine" -> "golang:1.27-alpine"), which flows through docs/server/swagger.json into sdk/go/openapi.json, openapi.yaml and the generated client. So even on a correct toolchain, verify's diff fails:

-  "description": "... Examples: \"golang:1.27-alpine\", ...   (freshly generated)
+  "description": "... Examples: \"golang:1.26-alpine\", ...   (committed)

Regenerated with task sdk-generate. It's a one-line change in each of the three files.

Type of change

• Bug fix

Test plan

• Unit tests (task test)
• Linting (task lint-fix)

Reproduced both on a clean checkout of main. Under Go 1.26 you get the toolchain error; under 1.27 you get the diff. With this change, on Go 1.27:

bash ./sdk/go/verify.sh   → rc=0
task sdk-test             → rc=0
task sdk-lint             → rc=0

I can't exercise the workflow's setup-go step locally, so that half is reasoned from the error rather than executed - worth a sanity check from someone who can re-run the job.

Does this introduce a user-facing change?

No. sdk/go/go.mod is untouched, so the SDK's minimum Go version for consumers is unchanged.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.91%. Comparing base (7e52ab9) to head (0c9da28).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6645      +/-   ##
==========================================
- Coverage   78.92%   78.91%   -0.01%     
==========================================
  Files         782      782              
  Lines       78053    78053              
==========================================
- Hits        61601    61599       -2     
- Misses      16447    16449       +2     
  Partials        5        5              

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