fix: move documented examples under integrations

[rlippmann]

Summary

• move documented host integration examples under examples/integrations/
• update README paths and examples index links to match the new structure
• ensure package contents include documented integration examples via explicit files entries
• keep build/test stable by limiting integration TS compile scope
• keep package version at 0.7.2 (restore from transient 0.7.3)
• fix CI Next.js integration workflow path after directory move
• fix Next.js integration local package dependency path after directory move

Why

• release validation showed example structure inconsistency and packaging/docs mismatch
• CI still referenced the pre-move examples/nextjs-basic path
• Next.js example still referenced old local file: dependency depth after moving into examples/integrations/
• this makes integration examples consistently organized, shipped, and validated in CI

Scope checklist

• Diff is minimal and scoped to the requested behavior
• Python/spec parity is preserved (or mismatch is explicitly documented)
• Fixture semantics are respected (exact string vs non-empty null rule)
• No unrelated refactors
• Relevant validation was run (npm test for behavior changes, or docs-only/no-runtime-change)

Notes

• no engine/parser/fixture semantics changed
• npm pack --dry-run includes:
  • examples/integrations/nextjs-basic/**
  • examples/integrations/node-basic/**
  • examples/integrations/vercel_ai_sdk_structured_output/**
  • examples/README.md

Validation details:

• npm test: passed
• Next.js integration checks: npm ci + npm run build passed in examples/integrations/nextjs-basic
• If not run, why: N/A