docs: record 2026-07-20 A2 re-confirmation state in validation matrix

Log-grep legs (MSI-X, xHCI IRQ) re-confirmed again this morning; login-based
legs still blocked by the concurrent .claude QEMU workload (SIGKILL of
competing guests); retry loop armed; IOMMU leg needs a redbear-full image.

local/docs/HARDWARE-VALIDATION-MATRIX.md

@@ -40,11 +40,18 @@
   death. See `local/docs/IRQ-AND-LOWLEVEL-CONTROLLERS-ENHANCEMENT-PLAN.md` § "Runtime proof
   status (2026-07-20)".
 - MSI-X (virtio-net) and xHCI interrupt-driven mode were re-confirmed on the current
-  `redbear-mini` ISO. Re-confirmation of the login-based legs (PS/2, timer, BOT) with the new
+  `redbear-mini` ISO — once more on 2026-07-20 ~09:10 JST via `test-lowlevel-controllers-qemu.sh`
+  (log-grep legs, unaffected by host contention).
+- Re-confirmation of the login-based legs (PS/2, timer, BOT) with the new
   harness is pending an uncontended host — the current build host runs a parallel QEMU-testing
-  workload that kills QEMU processes and stalls guest boots under load; boots reach getty but the
+  workload (a concurrent agent session under `~/.claude/jobs/` with its own QMP-controlled
+  guest) that SIGKILLs competing QEMU processes; boots reach getty but the
   login prompt is not observed within the timeout there. The ✅ marks above reflect prior
-  validation of those legs.
+  validation of those legs. A retry loop (`/tmp/opencode/a2-retry.sh`) is armed to run the
+  PS/2, timer, and USB-storage legs automatically once the foreign QEMU workload exits.
+- The IOMMU first-use leg currently skips on `redbear-mini` runs because
+  `build/x86_64/redbear-full/harddrive.img` is absent — a `redbear-full` build is required
+  to re-confirm that leg.
 - Display boots (`-vga std`) can freeze at the fbcond `Performing handoff` step (the
   `reopen_for_handoff()` path can block rather than return `EAGAIN` for retry). Headless
   (`-vga none`) boots avoid it. Tracked separately on the graphics stack.