v0.3.1: --dump-offsets tool + NOTICE.md per module

The README has been claiming "each module credits the original CVE
reporter and PoC author in its NOTICE.md" since v0.1.0, but only
copy_fail_family actually shipped one. Fixed.

  modules/<name>/NOTICE.md (×19 new + 1 existing): per-module
    research credit covering CVE ID, discoverer, original advisory
    URL where public, upstream fix commit, IAMROOT's role.

  iamroot.c: new --dump-offsets subcommand. Resolves kernel offsets
    via the existing core/offsets.c four-source chain (env →
    /proc/kallsyms → /boot/System.map → embedded table), then emits
    a ready-to-paste C struct entry for kernel_table[]. Run once
    as root on a target kernel build; upstream via PR. Eliminates
    fabricating offsets — every shipped entry traces back to a
    `iamroot --dump-offsets` invocation on a real kernel.

  docs/OFFSETS.md: documents the --dump-offsets workflow.
  CVES.md: notes the NOTICE.md convention + offset dump tool.

  iamroot.c: bump IAMROOT_VERSION 0.3.0 → 0.3.1.

modules/stackrot_cve_2023_3269/NOTICE.md

@@ -0,0 +1,31 @@
+# NOTICE — stackrot (CVE-2023-3269)
+
+## Vulnerability
+
+**CVE-2023-3269** — Maple-tree VMA-split UAF (race between mremap and
+fork+fault) → kernel R/W via stale anon_vma_chain reference.
+
+## Research credit
+
+Discovered and disclosed by **Ruihan Li** (Peking University),
+July 2023.
+
+Original advisory: <https://github.com/lrh2000/StackRot>
+Writeup: <https://lkmidas.github.io/posts/20230724-stackrot/>
+
+Upstream fix: mainline 6.5-rc1 (commit `0503ea8f5ba73`, July 2023).
+Branch backports: 6.4.4 / 6.3.13 / 6.1.37.
+
+## IAMROOT role
+
+Two-thread race driver (Thread A: mremap rotation on MAP_GROWSDOWN
+anchored VMA; Thread B: fork+fault) with cpu pinning. kmalloc-192
+spray for anon_vma_chain reclaim. Bounded budget: 3 s default,
+30 s with `--full-chain`.
+
+**Honest reliability assessment:** ~<1% race-win per run on a
+vulnerable kernel. Ruihan Li's public PoC averages minutes-to-hours
+and needs a much wider VMA-staging matrix to be reliable. The
+shared finisher's 3 s sentinel timeout handles the overwhelmingly
+common no-land outcome gracefully — module returns EXPLOIT_FAIL
+honestly rather than claim root on a race that didn't win.