docs(index): index edits go on main and get pushed

Sister projects are told to update their entry here whenever an indexed fact
changes, but that edit lands in this repo's own checkout — so a naive commit
writes it onto whatever branch scadaproj happens to be on. Observed 2026-07-27:
the OtOpcUa Sql driver's entry sat unpushed on feat/overview-dashboard for three
days, and the Mqtt entry was about to join it.

Records the procedure (stash, main, push, restore) and says to cherry-pick
stranded index commits rather than merge the branch they are stuck on.

Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW

CLAUDE.md

@@ -361,6 +361,32 @@ This file is meant to be re-scanned when `scadaproj` is opened in Claude Code:
 3. Keep the project set **curated** — only the SCADA/OT/Wonderware/OPC-UA family belongs here.
 4. Flag new duplicates/overlaps and namespace mismatches rather than silently merging them.
 
+### Index edits go on `main`, and get pushed
+
+Every sister project's `CLAUDE.md` tells it to update its entry here whenever a fact this
+index records changes. That edit lands in **this** repo, which has its own checkout — so a
+naive `git commit` writes it onto whatever branch `scadaproj` happens to be on, usually an
+unrelated feature branch, sometimes one with no upstream. The index then disagrees with
+reality for as long as that branch stays unmerged, which is the exact drift the rule exists
+to prevent, and it is invisible unless someone goes looking.
+
+**So: commit index edits on `main` and push them.** Stash or set aside unrelated work first
+— never commit an index edit onto a dirty branch — and restore the original branch after:
+
+```bash
+git rev-parse --abbrev-ref HEAD    # note it
+git checkout main && git pull
+#   …edit the entry…
+git commit -am "docs(index): <what changed about <project>>" && git push origin main
+git checkout -                     # restore
+```
+
+**Observed 2026-07-27:** the OtOpcUa `Sql` poll driver's entry had sat unpushed on
+`feat/overview-dashboard` since 2026-07-24 for exactly this reason, and the `Mqtt` driver's
+entry was about to join it. Both were recovered by cherry-picking onto `main` (`6ab50fe`,
+`591eaac`, `7dcd93c`) — **cherry-pick stranded index commits rather than merging the branch
+they are stuck on**, since that branch usually carries unrelated in-progress work.
+
 ## Other workspace projects with a CLAUDE.md (not indexed — promote on request)
 
 Listed so they can be pulled into the index above if you decide they belong.