add safe context sync script

saturn/README.md

@@ -31,6 +31,12 @@ The documentation is based only on stated facts. Missing details are recorded as
 - [Joplin Server](docs/joplin-server.md)
 - [Unknowns and clarification questions](docs/questions.md)
 
+## Workflow
+
+- Start Codex with `./start-codex.sh`.
+- Start Aider with `./start-aider.sh`.
+- Sync shared context only with `./sync-context.sh` from the repo root after updating `codex_context.yaml`.
+
 ## Known facts
 
 - The homelab has one known main server: Raspberry Pi 5.

saturn/sync-context.sh

@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+REPO_ROOT="$(git rev-parse --show-toplevel 2>/dev/null || true)"
+
+if [[ -z "$REPO_ROOT" ]]; then
+  echo "Not inside a git repository" >&2
+  exit 1
+fi
+
+if [[ "$(pwd)" != "$REPO_ROOT" ]]; then
+  echo "Run this script from the repo root" >&2
+  exit 1
+fi
+
+mapfile -t status_lines < <(git status --porcelain=v1 --untracked-files=all)
+
+for line in "${status_lines[@]}"; do
+  path="${line:3}"
+  if [[ "$path" != "codex_context.yaml" ]]; then
+    echo "Refusing to sync: only codex_context.yaml may be changed" >&2
+    exit 1
+  fi
+done
+
+git pull --rebase
+
+if git diff --quiet -- codex_context.yaml && git diff --cached --quiet -- codex_context.yaml; then
+  echo "No context changes to sync"
+  exit 0
+fi
+
+python3 -c "import yaml; yaml.safe_load(open('codex_context.yaml'))"
+git add codex_context.yaml
+git commit -m "update shared context"
+git push