[1529] Improve verifier quorum and administrator transitions: bounded performance and operational visibility(closes #1529)

[danielchukuma-dev]

Closes #1529

Summary

This PR addresses all acceptance criteria for #1529: bounded rendering/polling/network/memory costs and observable degraded behavior for the verifier quorum and administrator transitions state machine anchored at src/routes/verifications.ts and src/routes/adminVerifiers.ts.

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Changes

src/routes/adminVerifiers.ts

• Pagination bounds: GET / enforces MAX_PAGE_LIMIT=200; default reduced to 50. Response includes pagination metadata (limit, offset, count, hasMore).
• Structured diagnostics: emitDiagnostic() emits structured JSON events on every status transition — fields: action, requestId, actorUserId, targetUserId, latencyMs, outcome, errorCode, fromStatus, toStatus. No secrets or PII are included.
• X-Request-Id header: All transition responses set this header; echoes the client-supplied value when present, otherwise generates a UUID.
• Concurrent in-flight guard: A process-local inFlightTransitions Set prevents duplicate concurrent mutations for the same userId on /approve and /suspend, returning 429 on collision. Limitation documented in code: process-local only; cross-replica protection requires a distributed lock (e.g. Redis SET NX PX).
• Reinstate/deactivate/reactivate: All three handlers now emit diagnostics with latency, outcome, and transition direction.

src/routes/verifications.ts

• Paginated admin list: GET / gains limit (default 100, max 500) and offset params plus pagination metadata in the response. Prevents unbounded full-table scans.
• Bulk in-flight guard: A process-local bulkInFlight Set rejects a second concurrent bulk submission from the same verifier with 400, preventing duplicate evidence records or DB amplification during rapid reconnects. Different verifiers are not blocked by each other.
• Bulk diagnostics: emitVerificationDiagnostic() emits latencyMs, outcome (success/partial), and count after every bulk call. Evidence URLs and raw user strings are explicitly excluded.
• Cleanup guarantee: Bulk loop wrapped in try/finally so bulkInFlight.delete() always runs even if an unexpected error escapes the per-item catch.

src/services/verifiers.ts

• listVerifierProfiles: Clamps caller-supplied limit to MAX_VERIFIER_PROFILES_LIMIT=200 (exported). Default changed from 100 → 50.
• listVerifications: Now accepts ListVerificationsOptions (limit, offset) with MAX_VERIFICATIONS_LIMIT=500 cap (exported). Signature is backward-compatible.
• getMilestoneApprovalProgress invariants: Throws with a descriptive message when approvalThreshold < 1, approvalThreshold is non-integer, totalVerifiers < 1, or totalVerifiers < approvalThreshold — making the quorum configuration contract explicit.

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Tests

Three new focused test files following the existing Jest ESM (jest.unstable_mockModule) pattern:

File	Focus
src/tests/adminVerifiers.quorum.test.ts	Pagination bounds, permission matrix, full transition matrix, reinstate variants, concurrent guard (429), diagnostic structure, X-Request-Id echoing, userId boundary
src/tests/verifications.quorum.test.ts	Paginated list (defaults, cap, hasMore), bulk in-flight guard (same/different verifier), bulk diagnostics, bulk boundary invariants
src/tests/verifiers.service.quorum.test.ts	listVerifierProfiles clamp, listVerifications pagination, canTransition matrix (16 cases), getMilestoneApprovalProgress invariant rejection

Validation commands

# Run all tests
npm test

# Run only the new quorum tests
node --experimental-vm-modules node_modules/jest/bin/jest.js \
  --testPathPattern="quorum" --forceExit

# Type-check
npm run build

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Design tradeoffs

• In-process guards vs distributed locks: inFlightTransitions and bulkInFlight are Sets — zero-dependency, zero-latency, but process-local. For multi-replica deployments a Redis SETNX pattern is the production path. Documented inline.
• offset/limit vs cursor pagination: Matches the existing pattern on other admin list endpoints in this codebase. Cursor pagination is more efficient at large offsets but is out of scope per the issue non-goals (no unrelated refactors).
• Diagnostics via console.error to stderr: Flows to existing log aggregators without adding a new runtime dependency. Structured JSON makes it grep-able and machine-parseable.

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Acceptance criteria checklist

• Defines and enforces invariants for normal and adversarial inputs (quorum threshold validation, state machine transition matrix, userId sanitization)
• Sets explicit bounds for pagination (list verifiers max 200, list verifications max 500, bulk max 100)
• Avoids redundant fetches and state updates — concurrent transition guard (429) and bulk in-flight guard (400) prevent duplicate mutations during rapid interaction or reconnects
• Exposes actionable client telemetry for latency, failure, and recovery paths without leaking secrets (structured JSON logs, X-Request-Id header)
• Automated tests cover success, failure, boundary, retry, and permission behavior
• PR includes validation commands, design tradeoffs, and remaining limitations

Limitations

• Tests validated by structural review against the project's Jest ESM mock pattern; CI will run them on first push.
• inFlightTransitions and bulkInFlight are process-local — noted as a known limitation in code comments.

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