Add a reusable Graphile performance harness

[Zetazzz]

Responsibility

Adds reusable fresh-process Graphile benchmarking infrastructure. The runner accepts arbitrary serializable case definitions and delegates case-specific build and lifecycle validation to a dedicated worker entry.

Included here:

• fresh Node process and unique PID per measurement
• --expose-gc with deterministic GC calls
• build-only wall-clock timing
• memory snapshots, deltas, and peak RSS
• seeded scheduling and repetitions
• schema groups and schema-hash validation
• runtime query and case-specific validation contracts
• PostgreSQL fixture preparation
• atomic JSON reports and database URL redaction
• a minimal upstream Graphile baseline worker

Stack

This is the first PR in the new performance stack and targets main. Later stacked PRs can add their own benchmark suites without changing the core runner.

Not included

No product-specific benchmark suite, application preset, application plugin integration, dependency patch, or optimization conclusion is included.

Validation

• unit tests: 7 passed across 5 suites
• CJS and ESM build: passed
• ESLint: passed
• Prettier and git diff --check: passed
• frozen-lockfile install: passed
• real PostgreSQL upstream baseline smoke: passed
  • fresh worker process
  • runtime query passed
  • schema hash recorded
  • report contained no database URL

There are no temporary patches in this PR.