fix(magisk): scrub any competing /system/xbin/su; Verify fails on a non-Magisk su

[Jordan231111]

Symptom

Magisk shows "Abnormal State — a su binary not from Magisk has been detected" on a freshly-rooted instance.

Root cause (investigated per "look at the last commits")

• The competing su is /system/xbin/su — sha 185106…, 2,012,872 B = the engine''s classic-su binary (the old root method), left in the shared master Root.vhd.
• Git proves no commit changed su handling: bsr_magisk.ps1 has only two commits ever (ac2af27 + the adb fix), and the only commit touching system/xbin/su is ac2af27. The v11 adb fix didn''t write any su — it just let the pipeline complete, so Magisk finally booted and flagged the pre-existing leftover.
• Where that su came from: tests/Run-Live-E2E.ps1 rooted via the engine''s legacy classic-su path (-Action AdbRoot), which installs a setuid /system/xbin/su. Running it (a prior background re-root E2E) planted the su in the master.
• Two real gaps: Prep/Clean scrubbed only the bootstrap su (bsr_su), never a pre-existing /system/xbin/su; and Verify only swept for bsr_su''s hash, so a competing su passed silently.

Fix

• Prep + Clean now rm /system/xbin/su (+daemonsu) in the offline carve. Magisk''s own su (/system/bin/su→magisk, /sbin/su→magisk) is the only one. Re-running Clean repairs an already-rooted instance.
• Verify enumerates every su in the standard PATH dirs and FAILS on any that isn''t a symlink to magisk (new pure, unit-tested Find-StraySu). The scan is pushed as a script file (the inline loop''s ; didn''t survive PS→adb→device quoting).
• Run-Live-E2E.ps1 rewritten to drive the shipped bsr_magisk.ps1 -Action Auto pipeline and assert VERIFY PASS + no competing su across a reboot — correct package io.github.huskydg.magisk, revert via Magisk Undo. (It previously planted the competing su via classic-su.)

Verified live (Tiramisu64_9)

• Enhanced Clean scrubbed /system/xbin/su (stat → File not found), Root.vhd updated.
• Verify then reported competing su: none → VERIFY PASS (su -c id→uid=0, /system/bin/su→./magisk, no bsr_su traces).

Tests

• Run-Resolve-Tests.ps1: +7 Find-StraySu cases → 38/38
• Run-Tests.ps1 → 28/28; Check-Embedded-Sync.ps1 in sync (re-embedded blueStackRoot.cmd)