Implement `File.stat` method that performs an asynchronous `fstat` call on the open file descriptor, returning a `Stat` object populated with file metadata (device, inode, mode, link count, user, group, size, block size, block count). Refactor the existing `statPathCallback` into a generic `statCallback` shared by both `statPath` and the new `fileStat` function. Bump `MAX_METHODS_PER_CLASS` from 11 to 12 to accommodate the new foreign method slot. Add comprehensive test coverage including successful stat retrieval and error handling when called on a closed file.
Implement asynchronous stat() on File class returning a new Stat object with device, inode, mode, linkCount, user, group, specialDevice, size, blockSize, and blockCount fields populated from libuv uv_fs_stat callback. Register foreign method statPath_ in module registry, bump MAX_METHODS_PER_CLASS to 10, add Stat class to io.wren with indexed field accessors, update documentation index with Stat page, and include test coverage for stat on existing file and nonexistent path.
Add foreign class File with static open, read, size methods and instance methods for close, size, readBytes. Implement async file operations using libuv callbacks that resume fibers on completion. Introduce schedulerResumeError and resumeError_ to propagate I/O errors as fiber errors. Add setExitCode to CLI vm for runtime error exit handling. Bump MAX_METHODS_PER_CLASS from 2 to 9 to accommodate new File methods.
Introduce a new built-in "io" module exposing a File class with a static size(path) method that performs asynchronous filesystem stat via libuv. The method uses a foreign function startSize_ to initiate the stat request and resumes the calling fiber through the scheduler upon completion. Extend the scheduler with schedulerResumeDouble and schedulerResumeString to support resuming fibers with numeric or string results. Include the generated io.wren.inc source, update the Xcode project to compile io.c and io.wren.inc, register the module in modules.c, and add a test file verifying synchronous-style async size calls and error handling.
