Slate v2 Phase 9 Paste HTML Matrix

Supporting plan. For current queue and roadmap truth, see master-roadmap.md.

Goal

Start Phase 9 replacement-envelope expansion with one honest matrix slice for the paste-html family.

Scope

• add legacy paste-html coverage to the replacement compatibility matrix
• add current paste-html coverage to the same matrix
• sync scoreboard/docs if the slice lands cleanly

Constraints

• no fake direct parity claim between legacy broad HTML paste and current narrow explicit subset
• use the matrix to show what each side really proves
• keep verification on port 3010 for current local app runs

Evidence

• legacy paste-html already has Playwright tests for <strong> and <code>
• current paste-html now has browser proof for paragraph, link, strong, em, and code
• the replacement matrix currently omits the paste-html family entirely

Progress

• added one legacy paste-html row to the replacement compatibility matrix
• added one current paste-html row to the same matrix
• proved the expanded matrix through the cross-repo local runner
• synced the scoreboard and top-level v2 docs so Phase 9 is now the active program phase
• verification:
  • bash ./scripts/run-cross-repo-local.sh 3010 /examples/rich-inline ../slate 3210 /examples/search-highlighting "yarn build:slate-browser:playwright && yarn exec playwright test playwright/integration/examples/replacement-compatibility.test.ts --project=chromium --workers=1"