Add PulseOps benchmark evidence

[d3v07]

Summary

• Add article evidence documentation, benchmark reports, query-plan proof, observability notes, and safe migration documentation.
• Add reproducible benchmark/load scripts for ingest, hot tenant, dashboard, cache, worker catch-up, and backpressure paths.
• Add tenant isolation, idempotency, late event, worker restart, cache correctness, GraphQL authz, and unit tests.
• Preserve both clean full benchmark evidence and ingest-scale stress evidence, including the local 1000 RPS run that was not sustained.

Validation

• pnpm test
• pnpm test:integration
• pnpm test:load
• pnpm typecheck
• pnpm lint (warnings only)
• pnpm health
• pnpm db:verify:fresh
• RUN_ID=2026-06-16-clean-full-benchmark pnpm benchmark
• RUN_ID=2026-06-16-clean-full-benchmark ./scripts/capture-query-plans.sh

Reviewer starting points

• docs/benchmarks/2026-06-16-clean-full-benchmark.md
• docs/article-evidence.md
• docs/benchmarks/2026-06-16-ingest-scale-pulseops-benchmark.md
• docs/observability.md
• docs/migrations/safe-migration-example.md
• docs/query-plans/