chore: gitbot-fleet hygiene — Bustfile, findings-submissions doc, Fallback:Nix reconcile (#261)

Adds the missing Bustfile (completing the Dust/Bust pair), documents
findings-submissions as an automated data-sink branch, and reconciles the
robot-repo-automaton "Fallback: Nix" note to Guix-only (consistent with #260).

https://claude.ai/code/session_016R5WsMHtpnD8bmrkjFNFmg

Author: hyperpolymath

.machine_readable/contractiles/bust/Bustfile.a2ml

@@ -0,0 +1,26 @@
+# SPDX-License-Identifier: MPL-2.0
+# Bustfile — Breakage and Rollback Contract
+name = "bustfile"
+
+
+[bustfile]
+version = "1.0.0"
+format = "a2ml"
+
+[scenarios]
+bad-fix-script = "git revert the fix commit; fix scripts are idempotent, so a re-run after the fix is safe"
+dispatch-runner-failure = "halt dispatch-runner; inspect the JSONL manifest; a failed dispatch leaves the target repo untouched (no partial writes)"
+bot-repeated-failure = "auto-quarantine engages at 5+ failures or >30% false-positive rate; clear only after a root-cause fix"
+bad-bot-pr = "close the bot PR; revert any merged commit; confidence reverts via batch-rollback"
+
+[escalation]
+level-1 = "revert the offending commit (reversible, low blast radius)"
+level-2 = "quarantine the misbehaving bot (rate-limiter / quarantine subsystem)"
+level-3 = "batch-rollback the dispatch batch with confidence revert"
+level-4 = "force-push to main — PROHIBITED without explicit user confirmation"
+level-5 = "registry-level (delete/archive a repo) — human-only, never by AI"
+
+[reversibility]
+backup-before-destructive = true
+rollback-mechanism = "git-revert"
+batch-rollback-available = true

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`.

robot-repo-automaton/.claude/CLAUDE.md

@@ -57,7 +57,7 @@ Both are FOSS with independent governance (no Big Tech).
 ### Package Management
 
 - **Primary**: Guix (guix.scm)
-- **Fallback**: Nix (flake.nix)
+- **Fallback**: none — Guix-only (Nix retired 2026-06-05)
 - **JS deps**: Deno (deno.json imports)
 
 ### Security Requirements