Add zero-patch CNC scoped introspection package

[Zetazzz]

Summary

• Add the independently publishable graphile-scoped-introspection package under graphile/.
• Move the CNC Graphile plugin, preset, scoped SQL generator, PgService type augmentation, namespace/type closure validation, and gather/cache/watch tests into that package.
• Keep graphile-settings responsible only for makePgService normalization, convenience re-exports, and explicit ConstructivePreset wiring.
• Update the performance worker to import ScopedIntrospectionPreset directly from its owner package while continuing to use the narrow graphile-settings service factory.

Architecture

This implementation uses no pnpm patches and does not modify installed Graphile, Dataplan, or pg-introspection packages. The scoped SQL is CNC-owned, static, and parameterized; it is adapted from the MIT-licensed pg-introspection@1.0.1 query structure and the prior CNC implementation. It does not import private package subpaths or rewrite upstream SQL at runtime.

Stock-only configurations delegate to the upstream PgIntrospectionPlugin helper. Scoped configurations use the CNC query, and mixed stock/scoped services select independently. The replacement preset atomically disables the upstream plugin without mutating its singleton. A pinned graphile-build-pg@5.1.3 contract sentinel fails deterministically on version or gather-shape drift.

Client lifecycle

Introspection uses the normal three-argument withPgClientFromPgService(service, settings, callback) API. Each checkout returns to the upstream pool after the query; there is no destroy mode or custom release protocol. Final pool teardown remains the responsibility of PgService.release(), which the performance worker retains in finally for success and failure paths.

Validation

• graphile-scoped-introspection: 6 suites / 18 tests passed.
• graphile-settings: 6 non-database suites / 48 tests passed; real PostgreSQL ConstructivePreset build and runtime query passed.
• @constructive-io/perf-harness: 6 suites / 8 tests passed.
• CJS and ESM builds passed for all three affected packages.
• Affected ESLint, Prettier check, and git diff --check passed.
• pnpm install --frozen-lockfile and pnpm install --frozen-lockfile --offline passed.
• PostgreSQL 18.4 fresh-process smoke passed with distinct PIDs (16685, 16687), matching schema hash 6f78c926837733edca7c1706b1fde33bc260defb54d89000f6327cbeb2b1e1f3, runtime validation in both cases, and no database URL in the report.
• A scoped failure worker exited after the required-schema error, exercising its finally teardown path.
• The final diff against test/performance-harness-core contains no patch files, no patchedDependencies, and no .gitattributes patch rule.

Follow-up

When Graphile progressive introspection is available, CNC can replace this concentrated package boundary with the upstream implementation while leaving graphile-settings and the performance harness wiring narrow.