test: expand event publish helper coverage

[LyViolz]

Summary

• add focused coverage for node event deduplication, cache cleanup, heartbeat starters, and enhanced status fallbacks
• strengthen existing publisher tests to verify status and payload behavior
• cover the revised scope from the maintainer feedback on [Control Plane] Add tests for internal/events publish helpers (node/exec/reasoner) #394

Testing

• GOTOOLCHAIN=go1.25.0 go test ./internal/events/... -count=1
• GOTOOLCHAIN=go1.25.0 go test -race ./internal/events/... -count=1
• git diff --check
• internal/events coverage: 87.0% -> 97.2%

Fixes #394

[CLAassistant]

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[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	87.60%	87.40%	↑ +0.20 pp	🟡
sdk-go	93.00%	92.00%	↑ +1.00 pp	🟢
sdk-python	94.31%	93.73%	↑ +0.58 pp	🟢
sdk-typescript	91.68%	90.42%	↑ +1.26 pp	🟢
web-ui	84.76%	84.79%	↓ -0.03 pp	🟡
aggregate	85.81%	85.75%	↑ +0.06 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.

[santoshkumarradha]

I spot-checked the new event coverage locally and it looks fine, and the full CI surface is now green. At this point the remaining blockers are repo state rather than test content: license/cla is still pending, and after #1014 and #1015 landed this branch is now conflicting with current main. Please rebase on the latest main, rerun the checks, and once the CLA is signed this should be in good shape for a final pass.