WasmVM: WASI file descriptor operations incomplete (fcntl, openat, faccessat, lseek, read)

[NathanFlurry]

Summary

Several core POSIX file descriptor operations are not fully implemented in the WASI host, causing os-test failures. This includes fcntl() (file control), openat() (open relative to directory fd), faccessat() (access check relative to fd), lseek() (file seek), and read() edge cases.

Affected os-test cases

• basic/fcntl/fcntl
• basic/fcntl/openat
• basic/unistd/faccessat
• basic/unistd/lseek
• basic/unistd/read

Expected behavior

All file descriptor operations should work correctly through the WASI VFS layer.

Context

Discovered via os-test POSIX conformance suite. Tracked in posix-exclusions.json as fail / implementation-gap.