[codey] Add team pilot validation guide

[Conalh]

Summary

• adds docs/TEAM_PILOT.md with a concrete multi-repo trial path for teams evaluating PolicyMesh
• tells teams what to record from Action summaries and PR annotations
• makes paid-layer validation criteria explicit before SaaS work: shared baselines, central severity policy, exception ownership, cross-repo reporting, exports, APIs, and adoption blockers
• links the guide from README feedback flow and keeps that path covered by tests

Verification

• node --test test/workflow.test.mjs red before the guide existed, green after
• npm test (38/38)
• node dist/index.js audit --repo . --format json (rating none, 0 findings)
• git diff --check
• git diff --exit-code -- dist