content: CvRDT collaborative merge + 34 convergence tests (Phase 3 complete, 196/196)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plans/content-on-sx.md

@@ -19,7 +19,7 @@ injected adapter, not core.
 
 ## Status (rolling)
 
-`bash lib/content/conformance.sh` → **162/162** (Phase 1 complete + Phase 2: persist op log)
+`bash lib/content/conformance.sh` → **196/196** (Phases 1–3 complete: blocks, doc, render, api, persist op log, CRDT merge)
 
 ## Ground rules
 
@@ -67,8 +67,8 @@ lib/content/api.sx ── (content/edit) (content/render) (content/history) ─
 - [x] `(content/history doc)`, diff between versions
 
 ## Phase 3 — Collaborative merge (CRDT)
-- [ ] commutative/idempotent op merge
-- [ ] concurrent-edit tests (any order, double-apply → identical)
+- [x] commutative/idempotent op merge
+- [x] concurrent-edit tests (any order, double-apply → identical)
 
 ## Phase 4 — External sync + federation
 - [ ] Ghost/CMS sync via injected adapter (import/export)
@@ -77,6 +77,18 @@ lib/content/api.sx ── (content/edit) (content/render) (content/history) ─
 
 ## Progress log
 
+- 2026-06-07 — Phase 3 `crdt.sx` (**Phase 3 complete**): collaborative merge as
+  a state-based CvRDT. Merge is a join (lub) on a semilattice → commutative,
+  associative, idempotent by construction. Ordering = unique dense Logoot
+  position keys (cell = (digit actor), lexicographic); presence = OR-tombstones
+  (remove-wins); each field = an LWW-Register keyed by logical (ts, actor). Every
+  op contributes a PARTIAL element and per-id state is their join, so
+  update-/delete-before-insert are not lost. `crdt-materialize` bridges back to a
+  Phase-1 `CtDoc` (sort live elements by pos → blocks). Tests prove: ops in any
+  order converge, double-apply is a no-op, merge commutes/associates/is
+  idempotent, concurrent inserts order deterministically, same-field LWW by
+  (ts,actor), disjoint fields both survive, two divergent replicas converge both
+  ways. 34 tests; suite 196/196.
 - 2026-06-07 — Phase 2 `store.sx` (**Phase 2 complete**): op log + versioning
   over the persist event stream. `content/commit!` appends an edit op as a
   persist event to the doc's stream (`content:<id>`); the log is the source of