feat: add chaos/contract/load tests for issues #810 #811 #812 #805

[Ebuka042-pixel]

#810 – Chaos: x402 facilitator network partition mid-payment

• shared/tests/x402-network-partition-chaos.test.ts
• Partitions after verify-but-before-settle → 503, no phantom settlement
• checkFacilitatorHealth flips healthy→false; protected routes 503+Retry-After
• No order/tx recorded when settle cannot be confirmed
• Partition healing: health check restores healthy state and routes resume
• Facilitator errors not swallowed by global unhandledRejection handler

#811 – Chaos: audit-log disk pressure during rotation

• shared/tests/audit-log-disk-pressure-chaos.test.ts
• renameSync failure (ENOSPC) during rotation: hash chain stays valid
• appendFileSync ENOSPC surfaces to stderr; records not silently dropped
• Post-rotation-failure appends continue on existing file
• Verify path detects gap/tamper introduced by interrupted rotation
• Recovery: rotation succeeds once space returns; chain remains continuous

#812 – Contract test: x402 Facilitator getSupported payment-kinds

• shared/tests/x402-get-supported-contract.test.ts
• Pins OZ x402 Facilitator getSupported fixture (kinds/scheme/network shape)
• Empty or missing kinds array triggers boot-time fail-closed path
• Missing required fields (network, scheme) fail the contract
• Configured NETWORK must match at least one supported kind
• Provider-change detection: rename of 'kinds'/'scheme' caught in CI
• Documents how to refresh the fixture (curl + jq one-liner in header)

#805 – k6 load test: POST /agent/dispute-letter PDF generation

• load/dispute-letter.js
• Ramps VUs posting realistic audit results to /agent/dispute-letter
• Thresholds: p95 < 8000 ms, zero 5xx, zero empty/partial PDFs
• Health-check probe per iteration detects memory pressure / leaks
• Parameterized by BASE_URL, CAREGIVER_TOKEN, P95_LATENCY_MS
• Documented for manual and CI runs; three audit result variants

.gitignore: add generated/temp/snapshot/profile exclusions

• k6 results, vitest snapshots, test-data-*, PDFs, heap profiles

Closes #
closes #810
closes #811
closes #812
closes #805

What changed

How to test

Checklist

• CI passes (typecheck, lint, tests)
• No sensitive data files (data/spending.json, data/orders.json) committed
• PR linked to an issue

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