Two /move bugs on Windows:
1. Quoted absolute paths (e.g. /move "C:\...") were treated as relative
because surrounding quotes weren't stripped before path.isAbsolute().
2. /move before any model response threw ENOENT because the session
.jsonl file hadn't been created on disk yet (lazy-persist).
Changes:
- Extract stripOuterDoubleQuotes() helper in path-utils.ts, use in
handleMoveCommand() with empty-after-strip guard
- Guard session file rename with existsSync in moveTo(), leaving
artifact dir rename independently guarded
- Guard #rewriteFile() with hadSessionFile || hasAssistant to preserve
lazy-persist while still updating header cwd for existing files
- Add comprehensive test suite (13 tests) covering all moveTo() edge
cases including header-only sessions, deferred persistence, and
artifact migration
