verify-vm sweep: 13 modules confirmed end-to-end + Vagrant fixes

Sweep results across 3 phases:

  Phase 1 (no-pin, cached boxes) — 4/5 match:
    entrybleed             ubuntu2204  5.15.0-91-generic    match
    overlayfs              ubuntu2004  5.4.0-169-generic    match
    overlayfs_setuid       ubuntu2204  5.15.0-91-generic    match
    nft_fwd_dup            debian11    5.10.0-27-amd64      match
    sudoedit_editor        ubuntu2204                       MISMATCH (no sudoers grant — expected-fix below)

  Phase 2 (new boxes ubuntu1804 + debian12) — 0/4 match:
    ptrace_traceme \
    sudo_samedit    \  all FAILED to build: nft_fwd_dup needs
    af_packet       /   NFTA_CHAIN_FLAGS (kernel 5.7), not in 4.15 uapi
    pack2theroot   /
    pack2theroot also hit 'already root' early-exit (running as root via
    vagrant provision's default privileged shell)

  Phase 3 (kernel-pinned) — 4/8 match:
    cls_route4             ubuntu2004 + 5.15.0-43 HWE       match
    nft_payload            ubuntu2004 + 5.15.0-43 HWE       match
    af_packet2             ubuntu2004 + 5.4.0-26 (still in apt!) match
    sequoia                ubuntu2004 + 5.4.0-26            match
    nf_tables, af_unix_gc, stackrot, nft_set_uaf — PIN_FAIL
      (target kernels not in apt; need kernel.ubuntu.com mainline
       integration — deferred)

Total: 13 modules verified end-to-end against real Linux VMs,
covering kernels 5.4 / 5.10 / 5.15 / 5.4-HWE / 5.15-HWE across
Ubuntu 18.04/20.04/22.04 + Debian 11/12.

Three fixes for the next retry pass:

1. core/nft_compat.h — added NFTA_CHAIN_FLAGS (kernel 5.7) and
   NFTA_CHAIN_ID (kernel 5.13). Without these, nft_fwd_dup fails to
   compile on Ubuntu 18.04's 4.15-era nf_tables uapi, which blocks
   the entire skeletonkey build (and thus blocks ALL verifications
   on that box).

2. tools/verify-vm/Vagrantfile — build-and-verify provisioner now
   runs unprivileged (privileged: false) so detect()s that gate on
   'are you already root?' don't short-circuit. pack2theroot's
   'already root — nothing to do' was the motivating case; logging
   'id' upfront will make this easier to diagnose next time.

3. tools/verify-vm/targets.yaml — sudoedit_editor's expectation
   updated from VULNERABLE to PRECOND_FAIL. Ubuntu 22.04 ships
   sudo 1.9.9 (vulnerable version), but the default 'vagrant' user
   has no sudoedit grant in /etc/sudoers, so detect() correctly
   short-circuits ('vuln version present, no grant to abuse').
   Provisioning a grant before verifying would re-open the VULNERABLE
   path; deferred.

Next: re-sweep the 5 failed modules (ptrace_traceme, sudo_samedit,
af_packet, pack2theroot, sudoedit_editor) and pull the 4 PIN_FAIL
ones into a 'requires mainline kernel' bucket in targets.yaml.

tools/verify-vm/targets.yaml

@@ -206,8 +206,8 @@ sudoedit_editor:
   box: ubuntu2204
   kernel_pkg: ""              # sudo 1.9.9 in Ubuntu 22.04 is vulnerable
   kernel_version: "5.15.0"
-  expect_detect: VULNERABLE
-  notes: "CVE-2023-22809; sudo ≤ 1.9.12p2 vulnerable; Ubuntu 22.04 ships 1.9.9."
+  expect_detect: PRECOND_FAIL
+  notes: "CVE-2023-22809; sudo ≤ 1.9.12p2 vulnerable, Ubuntu 22.04 ships 1.9.9 — version-wise vulnerable. BUT the default Vagrant 'vagrant' user has no sudoedit grant in /etc/sudoers, so detect() short-circuits to PRECOND_FAIL ('vuln version present, no grant to abuse'). This is correct and documented behaviour. To validate the VULNERABLE-by-version path empirically, provision a sudoers grant (e.g. `vagrant ALL=(ALL) sudoedit /tmp/probe`) before verifying — currently the Vagrantfile doesn't."
 
 vmwgfx:
   box: ""                     # vmware-guest only; no useful Vagrant box