docs(fingerprint): parallel prompt in HARDWARE.md §5 + MIGRATION note

The feature commit updated the README table, template, ROADMAP and
HARDWARE-QUEUE but missed the canonical user-facing page: HARDWARE.md
§5 gets a "Parallel prompt" subsection (default, opt-out, structural
lockout safety, grep to verify, known leftover-prompt quirk) and the
option-summary table row; MIGRATION.md's fingerprint bullet points at
it. Doc-only, V0.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/MIGRATION.md

@@ -269,6 +269,9 @@ default yet.
   on whenever fprintd is enabled; Nomarchy forces PAM to follow the
   `pam` flag, but only after a **system** rebuild. Verify with
   `grep pam_fprintd /etc/pam.d/sudo` (should be empty when pam is off).
+  With pam on, the prompt accepts password *or* finger in parallel by
+  default (`fingerprint.parallel = false` for stock sequential) — see
+  HARDWARE.md §5.
 - **Browser profiles:** Nomarchy does not manage Chromium/Firefox state.
   Bookmarks/extensions live under `~/.config/chromium` (or
   `~/.config/google-chrome` / ungoogled paths if that was your previous