fix(upgrade): make snapshot paths Windows-safe (#167)

* fix(upgrade): make snapshot paths Windows-safe

Use a filesystem-safe UTC timestamp for new upgrade snapshot directories while retaining legacy ISO timestamp parsing. Normalize test paths with node:path so the Windows suite exercises the same behavior.

Co-Authored-By: claude-flow <ruv@ruv.net>

* fix(upgrade): sort snapshots by parsed timestamp

Order legacy colon and Windows-safe dash snapshot names chronologically so rollback and retention keep the actual newest snapshot across the migration boundary.

Co-Authored-By: claude-flow <ruv@ruv.net>

---------

Co-authored-by: nyxst4ck <nyxst4ck@users.noreply.github.com>
Co-authored-by: claude-flow <ruv@ruv.net>
Co-authored-by: nyxst4ck <289980115+nyxst4ck@users.noreply.github.com>

scripts/lib/snapshot.mjs

@@ -2,7 +2,7 @@ import { mkdirSync, writeFileSync, readFileSync, copyFileSync, existsSync, readd
 import { join } from "node:path";
 
 export function writeSnapshot({ homeDir, fromCommit, fromVersion, toVersion, extraFiles = [] }) {
-  const ts = new Date().toISOString().replace(/\.\d+Z$/, "Z");
+  const ts = formatSnapshotTimestamp(new Date());
   const root = join(homeDir, ".ocp", `upgrade-snapshot-${ts}`);
   mkdirSync(root, { recursive: true });
 
@@ -48,7 +48,10 @@ export function listSnapshots(homeDir) {
   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));
+    .sort((a, b) => {
+      const chronological = parseSnapshotTimestamp(a.name) - parseSnapshotTimestamp(b.name);
+      return chronological || a.name.localeCompare(b.name);
+    });
 }
 
 /**
@@ -107,9 +110,21 @@ export function gcSnapshots(homeDir, opts = {}) {
 }
 
 function parseSnapshotTimestamp(name) {
+  // Both legacy ISO names and Windows-safe names are supported.
   // upgrade-snapshot-2026-05-11T08:30:00Z → epoch ms
+  // upgrade-snapshot-2026-05-11T08-30-00Z → epoch ms
   const m = name.match(/upgrade-snapshot-(.+)$/);
   if (!m) return 0;
-  const t = Date.parse(m[1]);
-  return Number.isFinite(t) ? t : 0;
+  const raw = m[1];
+  const t = Date.parse(raw);
+  if (Number.isFinite(t)) return t;
+  const iso = raw.replace(/(T\d{2})-(\d{2})-(\d{2})Z$/, "$1:$2:$3Z");
+  const portable = Date.parse(iso);
+  return Number.isFinite(portable) ? portable : 0;
+}
+
+function formatSnapshotTimestamp(date) {
+  // Windows forbids ':' in directory names. Replacing only the time separators
+  // preserves chronological lexical order and keeps the timestamp readable.
+  return date.toISOString().replace(/\.\d+Z$/, "Z").replace(/:/g, "-");
 }