fix(api): detect stale/lagging RPC node in health check [BUG-109]

[Morenikeoa]

Bug

The /health endpoint's RPC check only verifies that getSlot() resolves within the timeout. An RPC node that is up and responsive but stuck (e.g. wedged sync, snapshot replay loop) will keep returning a valid — but non-advancing — slot, and the health check will report rpc: true forever. This defeats the purpose of the check for catching a degraded-but-responsive RPC provider.

Fix

Track the last (slot, checkedAt) reading in module state. On each check, if the new slot hasn't advanced past the last one and enough wall-clock time has elapsed for a live node to have produced new slots, mark checks.rpc = false and log the staleness with the elapsed time. The threshold is 30s — Solana's slot time is ~400-600ms even under congestion, so this is a wide margin, not a tight one. The first reading after a cache reset is always treated as healthy (no prior baseline to compare against).

__resetHealthCache() now also clears the staleness baseline for test isolation.

Test plan

• Added RPC staleness detection (BUG-109) describe block to tests/routes/health.test.ts with 3 cases (stale node flagged after 30s+ of no slot advancement, genuine slot advancement not flagged, rapid successive checks within the threshold not flagged) using vi.useFakeTimers().
• Verified the new tests are genuine regressions: reverted src/routes/health.ts via git stash, confirmed the staleness-detection test fails against the unfixed code, restored the fix.
• Full suite passes (297/298 — the 1 pre-existing failure is unrelated to this change, in adl.test.ts).
• tsc --noEmit clean.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: ddd733ef-4db3-404c-885b-449bb091921c

📥 Commits

Reviewing files that changed from the base of the PR and between b2751f4 and cee595d.

📒 Files selected for processing (2)

• src/routes/health.ts
• tests/routes/health.test.ts

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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