content: persist-backed op log + versioning + diff (Phase 2 complete, 162/162)

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` → **133/133** (Phase 1 complete: blocks + doc + render + api)
+`bash lib/content/conformance.sh` → **162/162** (Phase 1 complete + Phase 2: persist op log)
 
 ## Ground rules
 
@@ -63,8 +63,8 @@ lib/content/api.sx ── (content/edit) (content/render) (content/history) ─
 - [x] `api.sx` + tests + scoreboard + conformance.sh
 
 ## Phase 2 — Op log + versioning
-- [ ] edit ops as `persist` events; replay to any version
-- [ ] `(content/history doc)`, diff between versions
+- [x] edit ops as `persist` events; replay to any version
+- [x] `(content/history doc)`, diff between versions
 
 ## Phase 3 — Collaborative merge (CRDT)
 - [ ] commutative/idempotent op merge
@@ -77,6 +77,15 @@ lib/content/api.sx ── (content/edit) (content/render) (content/history) ─
 
 ## Progress log
 
+- 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
+  truth. `content/head` / `content/at b id seq` replay the op stream to the
+  latest / any version (materialised doc is a cache, never primary state).
+  `content/history` returns per-version metadata; `content/diff` /
+  `content/diff-versions` report added/removed/changed block ids. Backend is
+  injected via `(persist/open)` — content knows nothing about which backend.
+  Minimal persist load (event/backend/log/kv/api). 29 tests; suite 162/162.
 - 2026-06-07 — Phase 1 `api.sx` (**Phase 1 complete**): `content/*` facade over
   block + doc + render. `content/bootstrap!` registers the hierarchy;
   `content/edit` applies one op or an op stream; `content/render` picks the