docs: capture session context — licensing, deployment, package rename, npm publish plan

- specs/2026-03-19-licensing-model.md: full PolyForm Noncommercial dual-license spec
  including SPDX IDs, messaging constraints, website copy rules, compliance checklist
- plans/2026-03-19-vercel-deployment-notes.md: non-obvious deployment discoveries —
  outputDirectory iteration history, PostCSS .mjs fix, org migration secrets, domain
- plans/2026-03-19-npm-publish.md: step-by-step npm publish plan for both packages,
  CI integration, prerequisites
- plans/2026-03-19-langsmith-deployment.md: LangGraph Cloud deployment plan, agent
  architecture, environment variables, Vercel NEXT_PUBLIC_LANGGRAPH_URL update steps
- plans/2026-03-19-package-rename.md: decision record for @cacheplane scope rename,
  all affected files, lock file requirement

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: blove