Phase 6 Lane CI Ownership

Goal

Give the frozen Phase 6 benchmark and compatibility lanes a durable GitHub Actions home in .tmp/slate-v2 so the recent large-paste win stays measured, not local-only.

Scope

• add CI-usable scripts for the Phase 6 compat and huge-document lanes
• add a dedicated workflow that runs them on demand and on relevant mainline changes
• upload the huge-document benchmark JSON as an artifact

Non-Goals

• no broad CI redesign
• no full e2e matrix expansion
• no flaky benchmark threshold gate beyond command success and artifact capture

Acceptance

• a workflow exists under /Users/zbeyens/git/slate-v2/.github/workflows
• the workflow installs deps, prepares the Phase 6 runtime, and runs compat + huge-document lanes
• the huge-document benchmark JSON is uploaded
• local Phase 6 commands still work

Progress

• inspected current slate CI: only a generic matrix exists today
• confirmed current Phase 6 lanes only have local-oriented scripts
• decided on the smallest durable cut: factor reusable scripts first, then add one isolated workflow
• added reusable phase6:prepare, test:phase6:compat, and bench:phase6:huge-document scripts in package.json
• added CI workflow phase6-proof.yml
• verified the workflow-shaped commands sequentially: yarn phase6:prepare, yarn test:phase6:compat, and yarn bench:phase6:huge-document