refluxfs: drop the redundant standalone verify harness

The own-files reachability harness tools/verify-vm/refluxfs_verify.c is
superseded by the module itself: the safe default --exploit does the same
own-files reachability confirmation, and --full-chain provides the stronger
end-to-end proof (actual root). Remove the standalone and repoint the three
doc references (MODULE.md, RELEASE_NOTES.md, targets.yaml) at the module's
full-chain verification. The 4/4 own-files measurement it produced is kept
as a historical data point, just without the now-deleted reproducer.

No code depended on it; 148-test unit harness still green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0118iUgHY44hdRtANgyCmu7y

modules/refluxfs_cve_2026_64600/MODULE.md

@@ -205,13 +205,15 @@ qemu/KVM with 6 vCPUs — the stock GenericCloud installer layout, root on
 | Scratch cleanup | no artifacts left |
 | Build on el9 gcc | clean |
 
-**The underlying bug was separately confirmed winnable on that kernel**, using a
-VM-only harness driven at the public PoC's parameters (32 writers / 8 helpers,
-60 s budget — `tools/verify-vm/refluxfs_verify.c`): **4 out of 4 runs won**, with
-the first divergence after **69, 114, 170 and 494 rounds**. A racing `O_DIRECT`
-write landed on a still-shared block and rewrote the donor's on-disk bytes —
-the arbitrary-overwrite primitive, observed directly, contained to files the
-test user owned.
+**The underlying bug was separately confirmed winnable on that kernel.** The
+`--full-chain` run above is the definitive proof — the same reflink-CoW race
+rewrote `/etc/passwd` and landed root **3/3** (1244 / 3716 / 7913 rounds). An
+earlier *non-destructive* measurement, driven at the public PoC's parameters
+(32 writers / 8 helpers, 60 s) but confined to two files the test user owned,
+won **4/4** (first divergence after **69, 114, 170 and 494 rounds**): a racing
+`O_DIRECT` write landing on a still-shared block and rewriting the donor's
+on-disk bytes — the arbitrary-overwrite primitive, observed directly, contained
+entirely to attacker-owned files.
 
 Note carefully what this does and does not say. The shipped trigger **not**
 winning in 2 s on a kernel that is provably vulnerable is exactly the designed