fix: handle pipes without tools

[521Peter]

Summary

• reuse the normalized hasTools state when running a pipe
• avoid reading length from an omitted optional tools array
• add a regression test for running a pipe without tools

Testing

• pnpm --filter @baseai/core exec vitest --config vitest.node.config.js --run src/pipes/pipes.issue-155.test.ts
• verified the regression test fails before the fix and passes after it

The package-wide type check currently fails in the pre-existing src/pipes/pipes.test.ts file, and lint cannot resolve the repository's @langbase/eslint-config/library.js configuration.

Fixes #155