procfs: enumerate live SysV IPC objects

[brandonpayton]

Summary

• expose Linux-compatible /proc/sysvipc/msg, sem, and shm snapshots from the authoritative kernel IpcTable
• preserve truthful procfs inode identity for . and .. across procfs subdirectories
• cover live queue, semaphore, and shared-memory rows through a real guest on Node and Chromium

Stack

This PR is intentionally based on fix/procfs-fd-followed-stat at 9260b569d, the post-#907 port of #908. Landing order is #907, restacked #908, then this PR. It does not change the ABI and must not be merged before its base.

Validation

• kernel unit suite: 1,155 passed
• full Vitest: 1,333 passed, 2 expected failures, 67 skipped
• focused real guest: Node and Chromium passed
• Open POSIX: 174 passed, 0 failed, 3 expected failures, 2 skipped
• Sortix: 5,033 passed, 0 failed, 23 expected failures, 53 skipped
• libc: 303 passed, 0 failed, 20 expected failures, 1 flaky test passed
• ABI snapshot/generated bindings check passed
• pinned Rust 2024 rustfmt and git diff --check passed

Independent devil review found no issues at exact head c8e9d3f7c22fbef4745a628128120ec453e051ae. No merge action requested.