docs(claude): point sister-project-history detail to scadaproj skill dir

Claude-Session: https://claude.ai/code/session_01Wzg6NUCWHipSexLs2cgRFv

CLAUDE.md

@@ -54,6 +54,12 @@ through.
 about OtOpcUa changes here — remote/push status, the driver set, the Galaxy data flow,
 shared-lib consumption, or per-project commands — update the **OtOpcUa entry in
 `../scadaproj/CLAUDE.md`** in the same change so the index never drifts from this repo.
+**Since 2026-09-03 that entry is a short summary row.** The detailed OtOpcUa narrative —
+change history, live-gate records, redundancy/auth/ACL behaviour, and the per-issue
+consumer-impact record for ScadaBridge — lives in
+`../scadaproj/.claude/skills/sister-project-history/otopcua.md` (the `sister-project-history`
+skill). Append detail **there**; keep the index row to a few lines and only touch it when
+the summary itself (purpose, wire contract, driver set, auth posture, commands) changes.
 
 **The index edit belongs on `scadaproj`'s `main`, and must be pushed.** `scadaproj` is a
 separate repo with its own checkout, so committing there inherits whatever branch it
@@ -66,7 +72,7 @@ cd ~/Desktop/scadaproj
 git rev-parse --abbrev-ref HEAD            # note it, to restore afterwards
 git stash list                             # never commit onto a dirty unrelated branch
 git checkout main && git pull
-#   …edit the OtOpcUa entry in CLAUDE.md…
+#   …edit the OtOpcUa row in CLAUDE.md and/or .claude/skills/sister-project-history/otopcua.md…
 git commit -am "docs(index): <what changed about OtOpcUa>"
 git push origin main
 git checkout -                             # restore the original branch