chore(sdk-go): bump testify to v1.11.1

[santoshkumarradha]

Summary

• bump github.com/stretchr/testify in sdk/go from v1.8.4 to v1.11.1
• refresh go.sum after go mod tidy

Testing

• go test ./agent/...

[github-actions]

Performance

SDK	Memory	Δ	Latency	Δ	Tests	Status
Go	210 B	-25%	0.56 µs	-44%	✓	✓

✓ 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	87.00%	87.40%	↓ -0.40 pp	🟡
sdk-go	91.80%	92.00%	↓ -0.20 pp	🟢
sdk-python	93.87%	93.73%	↑ +0.14 pp	🟢
sdk-typescript	90.05%	90.42%	↓ -0.37 pp	🟢
web-ui	84.82%	84.79%	↑ +0.03 pp	🟡
aggregate	85.62%	85.75%	↓ -0.13 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.