feat(upgrade): add scripts/upgrade.mjs + scripts/lib/snapshot.mjs

Implements the upgrade dispatcher (noop / dry-run / light delegation /
full path) and the snapshot writer/reader/list module. Full path snapshots
plist + db + admin-key + openclaw.json before mutating, runs the 6 phases
(pre-flight, snapshot, fetch+install, reconfigure, restart, post-flight),
and emits a heads-up before launchctl bootout per
notify_before_prod_service_restart.md policy.

mockExec/mockDoctor injection points let tests verify the phase ordering
without touching the real shell. fresh_install + rollback paths are
deferred to Bundle 3.

No cli.js citation needed: this is OCP-internal upgrade tooling with no
corresponding cli.js operation.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/lib/snapshot.mjs

@@ -0,0 +1,50 @@
+import { mkdirSync, writeFileSync, readFileSync, copyFileSync, existsSync, readdirSync, statSync } from "node:fs";
+import { join } from "node:path";
+
+export function writeSnapshot({ homeDir, fromCommit, fromVersion, toVersion, extraFiles = [] }) {
+  const ts = new Date().toISOString().replace(/\.\d+Z$/, "Z");
+  const root = join(homeDir, ".ocp", `upgrade-snapshot-${ts}`);
+  mkdirSync(root, { recursive: true });
+
+  // Standard manifest files
+  writeFileSync(join(root, "from-commit.txt"), fromCommit + "\n");
+  writeFileSync(join(root, "from-version.txt"), fromVersion + "\n");
+  writeFileSync(join(root, "to-version.txt"), toVersion + "\n");
+
+  // Optional captures (best-effort, never fatal)
+  const tryCopy = (src, dst) => {
+    try {
+      if (existsSync(src)) copyFileSync(src, dst);
+    } catch { /* swallow */ }
+  };
+  tryCopy(join(homeDir, "Library", "LaunchAgents", "dev.ocp.proxy.plist"), join(root, "plist"));
+  tryCopy(join(homeDir, ".config", "systemd", "user", "ocp-proxy.service"), join(root, "service"));
+  tryCopy(join(homeDir, ".ocp", "ocp.db"), join(root, "db.bak"));
+  tryCopy(join(homeDir, ".ocp", "admin-key"), join(root, "admin-key"));
+  tryCopy(join(homeDir, ".openclaw", "openclaw.json"), join(root, "openclaw.json"));
+
+  for (const { src, name } of extraFiles) tryCopy(src, join(root, name));
+
+  return root;
+}
+
+export function readSnapshot(snapshotPath) {
+  const read = (n) => {
+    try { return readFileSync(join(snapshotPath, n), "utf8").trim(); } catch { return null; }
+  };
+  return {
+    path: snapshotPath,
+    fromCommit: read("from-commit.txt"),
+    fromVersion: read("from-version.txt"),
+    toVersion: read("to-version.txt")
+  };
+}
+
+export function listSnapshots(homeDir) {
+  const root = join(homeDir, ".ocp");
+  if (!existsSync(root)) return [];
+  return readdirSync(root)
+    .filter(name => name.startsWith("upgrade-snapshot-"))
+    .map(name => ({ name, path: join(root, name), mtime: statSync(join(root, name)).mtimeMs }))
+    .sort((a, b) => a.name.localeCompare(b.name));
+}