docs: document findings-submissions as an automated data-sink branch

Records that findings-submissions is a long-lived automated channel (the
Hypatia Finding Submitter pushes findings JSON to it) and must not be merged,
deleted, or branch-hygiene'd during reconciliation sweeps.

https://claude.ai/code/session_016R5WsMHtpnD8bmrkjFNFmg

Author: claude

docs/findings-submissions-branch.md

@@ -0,0 +1,21 @@
+<!-- SPDX-License-Identifier: MPL-2.0 -->
+<!-- SPDX-FileCopyrightText: 2026 Jonathan D.A. Jewell (hyperpolymath) -->
+
+# The `findings-submissions` branch
+
+`findings-submissions` is an **automated data-sink branch**, not a feature
+branch. The *Hypatia Finding Submitter* pushes scan-finding JSON to it on a
+schedule (commits titled `findings: <repo> @ <date>`), accumulating the raw
+findings stream that feeds the fleet's review queue.
+
+## Do not reconcile it
+
+- **Do not merge it into `main`.** It carries tens of thousands of lines of
+  findings JSON; merging would pollute `main` with transient data.
+- **Do not delete it.** It is an active channel — the submitter pushes to it
+  continuously and downstream tooling reads from it.
+- **Do not rebase/squash/branch-hygiene it.** Its divergence from `main` is
+  intentional and expected.
+
+Treat it like a queue, not a contribution. It is deliberately long-lived and
+divergent from `main`.