Fix packaged MCP smoke ownership checks

[baron]

Summary

• replace active UNIX-socket ownership probes with passive macOS libproc inspection
• tie the launched listener to the exact current socket inode through the existing owner-only, flock-held ownership lock
• preserve the full signed/notarized packaged-app windows roundtrip for Tip, stable release, promotion, and release-candidate smokes
• add zero-connection, wrong-owner, stale replacement, and bound-but-not-listening replacement regressions

Root cause

The packaged smoke ownership verifier connected to the production bootstrap socket only to read LOCAL_PEERPID, then closed without sending the newline-delimited bootstrap handshake. The app serializes handshake I/O, so those empty clients queued ahead of the real rpce-cli windows request and repeatedly produced BootstrapSocketServer: failed to read handshake, timing out Tip smoke after signing/notarization had already succeeded.

Safety

• no timeout increases, sleeps, smoke removal, unsigned artifacts, or signing bypasses
• exact launched PID/executable, owner-only directory/socket/lock, sole listener claimant, device/inode identity, held lock vnode, and stable snapshots remain fail-closed
• macOS libproc ABI sizes/offsets are asserted and self-tested in the packaged smoke
• official stable and Tip paths share the fixed smoke helper

Validation

• focused Python ownership tests: 3 passed
• full Scripts/test_release_tooling.py: 76 passed
• make dev-test FILTER=BootstrapSocketOwnershipTests: 7 passed
• make dev-lint: passed
• make dev-release-preflight: passed
• git diff --check and Python compilation: passed

Release evidence

• Fix bundled Codex release signing #606 signing/notarization fix is already on main and exact-main official Release Candidate packaging passed
• two Tip runs subsequently passed signing/notarization and failed only in this post-sign packaged smoke, matching this root cause exactly