fix: reduce AIC guardrail listArtifacts fan-out and add in-loop rate-limit backoff

[Copilot]

Under high run frequency + cold cache, the daily AIC guardrail produces an O(N×M) listArtifacts fan-out (N concurrent activations × M uncached prior runs), all drawing from the shared GITHUB_TOKEN core budget (~15k/hr). In a real incident this consumed ~50% of the hourly budget, starving unrelated critical steps (e.g. build-provenance attestation) with HTTP 403.

Changes

restore_aic_usage_cache_fallback.cjs — widen cross-branch search

• MAX_RUNS_TO_SEARCH: 5 → 20. The fallback searches recent completed runs for the aggregate aic-usage-cache artifact; 5 was too narrow for repos with high PR branch churn. At 20, PR-branch activations reliably find the artifact and populate the local cache before the guardrail loop runs, reducing per-run listArtifacts calls to zero on a warm aggregate cache.

check_daily_aic_workflow_guardrail.cjs — in-loop rate-limit backoff + consumption output

• RATE_LIMIT_RECHECK_INTERVAL = 5: after every 5 cache-miss artifact inspections the loop re-reads getCoreRateLimitSnapshot. Since all concurrent activation jobs share the same budget, a concurrent drain shows up here; if remaining < RATE_LIMIT_RESERVE the loop halts early with truncatedByRateLimit = true. This is the cross-run coordination mechanism without requiring shared state.
• daily_ai_credits_api_consumed step output: exposes the per-run before/after rate-limit delta so downstream monitoring can aggregate total guardrail cost across runs.

// After every RATE_LIMIT_RECHECK_INTERVAL cache-miss inspections:
const freshRateLimit = await getCoreRateLimitSnapshot(githubClient);
if (freshRateLimit.remaining < RATE_LIMIT_RESERVE) {
  truncatedByRateLimit = true;
  break;
}

Tests

• New test: main() stops after exactly 5 inspections when the in-loop re-check returns below-reserve remaining (7 candidate runs, only 5 inspected).
• New test: daily_ai_credits_api_consumed output equals the before–after rate-limit delta.

[github-actions]

🤖 PR Triage — Run §28715668077

Field	Value
Category	bug
Risk	🟡 Medium
Score	20/100
Impact	14/50
Urgency	4/30
Quality	2/20
Action	close

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