Slate v2 Phase 9 Plaintext / Read-only Family

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

Goal

Widen the replacement envelope for the simple editorial family:

• plaintext
• read-only

Scope

• add current v2 plaintext and read-only example surfaces
• add replacement-matrix rows for those current surfaces
• add the minimal slate-react Editable support needed for read-only truth
• sync scoreboard and family ledger if the slice lands

Constraints

• no fake richtext parity claim
• keep the package change as small as possible
• use current port 3010 for current local proof

Progress

• added current plaintext and read-only example surfaces in /Users/zbeyens/git/slate-v2/site/examples/ts/
• added JS mirrors and example registry entries
• proved current plaintext and current read-only through the replacement matrix
• widened the matrix further with matching legacy plaintext and read-only rows
• synced the scoreboard, family ledger, migration story, and current-surface docs
• verification:
  • bash ./scripts/run-cross-repo-local.sh 3010 /examples/plaintext ../slate 3210 /examples/plaintext "yarn build:slate-browser:playwright && yarn exec playwright test playwright/integration/examples/replacement-compatibility.test.ts --project=chromium --workers=1"