session-memory: Read-before-Edit reflex + curated pattern (WP-0008)

Acts on the #1 friction finding. T01: added a data-cited Read-before-Edit /
re-read-on-stale reflex to AGENTS.md (top error: 'File has not been read yet',
12/27 sessions). T02: captured it as a curated SolutionPattern
(sp-problem-file_not_read-edit, approved/distribution_ready) with real
resolutions + per-flavor hints, so Distribute proposes it across repos/flavors —
closing assess->curate->distribute on a real pattern. Suite 126/126.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

AGENTS.md

@@ -34,6 +34,18 @@ green), and for pipeline changes do a live `ingest → detect → curate` pass a
 the local store. See `session_memory/README.md` for the full layout and the
 detect → curate → distribute flow.
 
+### Editing files — Read before you Edit
+
+**Read a file (or the region you'll touch) before Edit/Write.** The most common
+error across our own captured coding sessions was *"File has not been read yet.
+Read it first before writing to it"* — 12 of 27 real sessions, 8 repos
+(`docs/ASSESSMENT-infra-friction.md`). Two cheap reflexes eliminate it:
+
+- **Read → then Edit/Write.** Don't blind-write a file you haven't read this
+  session; the edit tools reject it and the retry wastes a turn.
+- **On `File has been modified since read`, re-Read then re-Edit.** A stale read
+  means the file changed under you — refresh before retrying, don't loop.
+
 ---
 
 ## State Hub Integration