docs: flip stale status markers across the tracks (audit found 23)

An all-tracks docs-vs-code audit (the same method that caught the storage
drift) found 23 confirmed inaccuracies where a doc's build-status claim no
longer matches the source — status markers that were never flipped after a
track landed, and a few paths left over from completed flag-days. All verified
against the code before editing; docs only, no behavior change.

The systemic ones:
- IOMMU enforcement (driver-model.md, drivers.md): docs said enforcement was
  not built and "device_claim = ring 0" / "memory-safe is not true yet". It is
  built (per-device VT-d/AMD-Vi domains programmed at device_claim, -ECONFINE
  rollback, dma_alloc buffers bound and torn down at death; fail-open only with
  no IOMMU). Restated; M16 marker flipped to done.
- The FHS flag-day paths: /etc/devices.csv -> /system/configuration/devices.csv
  (devices-csv.md, new-driver-checklist.md, device-manager.md), /var/log ->
  /system/logs (logging.md, new-driver-checklist.md), /mnt/usb -> /volumes/usb
  (process-management.md). Following the old paths silently breaks driver match.
- protocol-namespace P4 "remaining" -> landed (only P5 remains); shared-fate
  fan-out "not yet enforced" -> enforced; wall_clock "not built" -> built;
  SMP affinity + fault-recovery "left" -> built; process_enumerate raw-pointer
  trust model -> checked copyToUser/EFAULT; bounds.md maximum_devices static
  hole -> dynamic per-registrar quota; init spawns fat -> volume-manager;
  config "hardcoded, move to /etc" -> already CSV data files; vdso.md three-
  value call; zig-self-hosting library/ layout; python argv "new" -> built.

Found and fixed by a multi-agent audit across 12 doc clusters, each finding
adversarially verified against the source.

docs/os-development/threading.md

@@ -84,7 +84,7 @@ address space. Threads deliberately remove that boundary *within* a process:
   there is no isolation **between** threads.
 - Threads share fate — by contract: a fault in any thread, or a "kill the process"
   decision, takes down **all** of them, so restartability lives at the process level,
-  not the thread level. (The kernel does not yet enforce this fan-out — see the
+  not the thread level. (The kernel enforces this fan-out — see the
   Lifecycle note under
   [Interaction with the rest of the kernel](#interaction-with-the-rest-of-the-kernel).)
 - Shared mutable state reintroduces data races — the failure class the