test(harness): cover raw result text and failure type serialization

[FriendlyPasser]

Summary

Adds table-driven tests for Result.Text() raw text preservation and JSON serialization/round trips for all six FailureType constants and the zero value.

This PR covers only the claimed sdk/go/harness/result_test.go subtask of #404. No production code changes.

Type of change

• Tests only

Test plan

Commands run from sdk/go:

• gofmt -w harness/result_test.go
• go test ./harness -run '^(TestResultTextReturnsRawResult|TestFailureTypeJSONSerialization)$' -count=1 -v — all 11 cases passed.
• TMPDIR=/private/tmp go test ./harness/... -count=1 -cover — passed; 92.3% package coverage.
• golangci-lint run --new-from-rev=HEAD~1 ./harness/... — passed.

Additional validation:

• Python SDK: 2364 passed, 4 skipped.
• TypeScript SDK: 970 passed.
• Web UI: 700 passed; build passed.
• Python lint passed.

Full-repository checks were not entirely green on macOS:

• ./scripts/test-all.sh stopped at an existing control-plane test requiring Linux /proc process-environment access. Remaining component suites were run separately.
• make lint reported existing Go issues outside this change.
• An existing harness cancellation test failed during a concurrent run; the full harness suite passed on a separate rerun.
• TMPDIR=/private/tmp avoids an existing macOS /var versus /private/var path comparison failure.

Test coverage

• I ran tests for the surface(s) I changed locally.
• New code paths are covered by tests in this PR (no bare additions). This PR adds tests only.
• The coverage gate check is green in CI before requesting review.

No production code was removed, and coverage-baseline.json was not changed. The 92.3% result is local harness package coverage; the repository-wide coverage gate still needs to run in CI.

Checklist

• I have read CONTRIBUTING.md (if present) and docs/DEVELOPMENT.md.
• Commits are signed and follow conventional-commits style.
• I have linked any related issues.

Read CLAUDE.md, AGENTS.md, and docs/CONTRIBUTING.md. The commit follows conventional-commits style but is not cryptographically signed.

AI-assisted implementation, reviewed and tested locally.

Related issues / PRs

Refs #404 — only the sdk/go/harness/result_test.go subtask.

[CLAassistant]

All committers have signed the CLA.

[santoshkumarradha]

Looks good. These tests clearly pin Result.Text() to the raw result and cover every current failure-type JSON value. The focused tests pass locally. I also ran the broader harness package; its only failure was an unrelated macOS /var versus /private/var temp-path assertion.

[github-actions]

Performance

SDK	Memory	Δ	Latency	Δ	Tests	Status
Go	170 B	-39%	0.39 µs	-61%	✓	✓

✓ No regressions detected

[github-actions]

📊 Coverage gate

Thresholds from .coverage-gate.toml: per-surface ≥ 84%, aggregate ≥ 85%, max per-surface regression ≤ 1.0 pp, max aggregate regression ≤ 0.50 pp.

Surface	Current	Baseline	Δ
control-plane	87.80%	87.40%	↑ +0.40 pp	🟡
sdk-go	93.10%	92.00%	↑ +1.10 pp	🟢
sdk-python	94.72%	93.73%	↑ +0.99 pp	🟢
sdk-typescript	91.72%	90.42%	↑ +1.30 pp	🟢
web-ui	84.77%	84.79%	↓ -0.02 pp	🟡
aggregate	85.89%	85.75%	↑ +0.14 pp	🟡

✅ Gate passed

No surface regressed past the allowed threshold and the aggregate stayed above the floor.

[github-actions]

📐 Patch coverage gate

Threshold: 80% on lines this PR touches vs origin/main (from .coverage-gate.toml:thresholds.min_patch).

Surface	Touched lines	Patch coverage	Status
control-plane	0	—	➖ no changes
sdk-go	0	—	➖ no changes
sdk-python	0	—	➖ no changes
sdk-typescript	0	—	➖ no changes
web-ui	0	—	➖ no changes

✅ Patch gate passed

Every surface whose lines were touched by this PR has patch coverage at or above the threshold.