🐛 fix(ai): harden Pi compatibility loader

[zrr1999]

Summary

• route the Baidu OneAPI compatibility extension through @earendil-works/pi-ai/compat factories so Pi's Jiti root alias cannot rewrite lazy API subpaths to dist/compat.js/api/*
• keep OpenAI SDK log suppression active across lazy setup and concurrent stream lifetimes without overwriting external log-level changes
• replace the handcrafted Jiti alias fixture with a fast regression test using the real Pi production loader and a local mocked Responses SSE transport
• reject unsupported Pi runtime imports across compatibility entrypoint graphs, including relative modules and workspace exports

Validation

• pnpm test test/pi-compatibility-loader.test.ts test/architecture-ratchets.test.ts test/spark-cli.test.ts (48 passed)
• pnpm --filter @zendev-lab/spark-ai run check (29 files type-clean, 6 tests passed)
• pnpm run check:static
• pnpm install --frozen-lockfile
• full root suite before publication: 1,543 passed, 2 skipped

Notes

• @earendil-works/pi-coding-agent is a root test-only dependency declared as ^0.82.1; Spark runtime packages retain the existing Pi AI kernel.
• no network requests are made by the loader regression test.
• this is a Spark-side compatibility fix; no upstream Pi changes are included.