design: the preflight mockup goes - the page was dropped on 2026-10-13

Owner, 2026-10-18: "Чисти этот хвост." Preflight as a page of its own was
dropped on 2026-10-13 (roadmap.md § Dropped): its installation checks went
to Server › Health (health-setup-checks, 2.11.0) and its test e-mail to a
form of its own (test-email, 2.12.0). The mockup still drew it and every
mockup's navigation still linked it.

- panel/src/preflight.html and its built page deleted; build.py's Server
  group loses the entry, and the 39 pages are rebuilt (each one only loses
  that link, in the navbar and the touch menu).
- check.py --write: outlines.json loses the "preflight" key; 31 screens,
  0 violations.
- index.html and panel-redesign.md § Room for roadmap items no longer list it.

The guard's deferredScreens entry goes in the next commit, on its own.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/plans/panel-redesign.md

@@ -238,7 +238,6 @@ Drawn and not built (`deferredScreens` in the guard tests):
 |---|---|---|
 | `in-queue` | [queue-table](../roadmap.md#queue-table): the queue as a table from `postqueue -j`, and an Inbound › Queue | undecided; Outbound › Queue shows postqueue's listing in a log pane (`outlineExempt`) |
 | `in-quarantine`, `in-quarantine-message` | inbound-quarantine, an idea off the roadmap ([its notes](inbound-quarantine.md)) | its open questions stay open; the mockup assumes SelfPost-held mail, release to upstream, 14 days, delegated like the rest of Inbound |
-| `preflight` | preflight as a page of its own, dropped 2026-10-13 ([roadmap](../roadmap.md#dropped-with-the-condition-for-return)); its checks went to Server › Health, the test e-mail to its own form | a leftover of a dropped item |
 
 The sibling strip under the navbar holds five or six entries per group without
 wrapping; Inbound would reach five (Domains · Log · Queue · Quarantine ·