Move scoped introspection benchmark to TypeScript and keep results local

[Zetazzz]

The scoped introspection benchmark from #1823 kept one run's CSV/environment JSON in source control and used a CommonJS script that required an absolute checkout path. Move the runner to src/benchmarks/scoped-introspection/run.ts, compiled by the existing CJS/ESM build, and expose pnpm --filter @constructive-io/perf-harness scoped:introspection with an optional --output directory. The stock/scoped experiment, validation, SQL diagnostics, and database cleanup are preserved.

Remove the recorded CSV and environment JSON, ignore the default generated-results directory, and retain the dated methodology, historical performance summary, environment details, and links to the original artifacts at their fixed commit. The new validation results remain local; the historical performance figures are unchanged.

Validation:

• Frozen-lockfile install and CJS/ESM builds passed.
• All 100 perf-harness tests passed, including import safety and CLI argument/output-path checks.
• Ran the compiled entrypoint against local PostgreSQL: all 42 measured samples across 0/10/50 unrelated schemas passed schema/runtime validation; SQL plans were written and the temporary database was dropped.
• Focused ESLint and git diff --check passed.

[tenki-reviewer]

Review complete. No issues found — approved ✅.

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This PR introduces packages/perf-harness, a performance-harness package focused on measuring scoped vs stock introspection cost. The core is src/benchmarks/scoped-introspection/run.ts, which executes both introspection variants against a seeded catalog fixture, captures environment/Postgres metadata before and after runs, computes median timings over warmup+measured repetitions, and writes results. A benchmarks/scoped-introspection.cjs provides the runnable entry, backed by environment and sample CSV fixtures, a written-up benchmark report, and a .gitignore for generated results.

Files	Change
src/benchmarks/scoped-introspection/run.ts	Implements the scoped vs stock introspection benchmark driver, sampling, seeding, and result persistence.
benchmarks/scoped-introspection.cjs + docs/env/samples	Provides the runnable entrypoint and its environment, sample CSV, and markdown report fixtures.
tests/entrypoints.test.ts	Verifies the package's CLI/entrypoint wiring.
package.json, README.md, .gitignore	Scaffold the new package, document usage, and ignore generated result artifacts.

Review of the changed lines surfaced no correctness, security, concurrency, or performance defects that met the confidence threshold after adjudication; the candidate observations were rejected as not actionable within the diff.

_{Reviewed commit: 4fd8f7b}