content: by-id ops (update/delete) act tree-wide — fixes op-log no-op on nested blocks + 4 tests (750/750)

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` → **746/746** (Phases 1–4 COMPLETE + ~34 extensions, hardened: HTML/SX escaping, Markdown render + import/export incl. tables & frontmatter (full round-trip), CvRDT flat + nested-tree + durable replication, tree-aware validation, snapshot cache, doc metadata, plain-text render, nested block trees + deep editing + flatten + relative reorder, doc stats + summary + multi-doc index, table + callout + media blocks, HTML page wrapper + SEO page, doc composition + id-remap, portable data + wire serialization, block query + transforms + find/replace, TOC + anchored headings + outline, normalization)
+`bash lib/content/conformance.sh` → **750/750** (Phases 1–4 COMPLETE + ~34 extensions, hardened: HTML/SX escaping, Markdown render + import/export incl. tables & frontmatter (full round-trip), CvRDT flat + nested-tree + durable replication, tree-aware validation, snapshot cache, doc metadata, plain-text render, nested block trees + deep editing + flatten + relative reorder, doc stats + summary + multi-doc index, table + callout + media blocks, HTML page wrapper + SEO page, doc composition + id-remap, portable data + wire serialization, block query + transforms + find/replace, TOC + anchored headings + outline, normalization)
 
 ## Ground rules
 
@@ -113,6 +113,14 @@ lib/content/api.sx ── (content/edit) (content/render) (content/history) ─
 
 ## Progress log
 
+- 2026-06-07 — Hardening: fixed a real layer seam (surfaced in the architecture
+  review) — by-id ops (update/delete) now act TREE-WIDE. `ct-replace-id` /
+  `ct-remove-id` (doc.sx) descend into any block carrying a `children` list, so
+  the persist op-log and `content/edit` correctly reach blocks nested in
+  sections (previously a silent no-op). `doc-move` stays top-level (guarded by
+  doc-find); insert/move remain positional. Inline section detection (no
+  section.sx dep). +4 store regression tests (nested update/delete via op-log +
+  replay-to-seq). Full gate over foundational doc.sx: 750/750.
 - 2026-06-07 — Hardening: audit confirmed the persist op-log (store.sx) carries
   every block type through commit → replay (op-insert carries the block
   instance; updates apply by id). Locked with +4 store tests (callout/media