Merge main into the teams branch

Two conflicts, and both were two people counting the same things differently
rather than disagreeing about what the code should do.

PhoneShell's header comment. The branch made "the five hub screens"
numberless, because TEAMS made it six and a number in that sentence had
already gone stale once. Main corrected "three destinations" to "two" in the
same sentence, because giving a shell the whole phone took the terminal out of
the set the header is drawn on. Both are right and neither noticed the other:
the header now stays on the hub's screens and on the two top-level
destinations, which is Hosts and Keychain.

The manual checks. Both sides appended a Phase 10 — main added the software
keyboard and the phone's terminal surface as 10 and 11, the branch added
Teams. Nothing about them overlaps, so the resolution is to keep all three in
the order they were written and renumber Teams to Phase 12, its subsections
and the one cross-reference inside 12.1 with it. Main's two phases keep the
numbers they already carry in its history, since renumbering those would move
headings somebody may already have linked to.

Everything else merged without a conflict, and the two places worth checking
afterwards both held: IsMoreSurface and the first case of
PhoneShell.OnBackRequested each kept ShellScreen.Team alongside main's edits.
Those two are one fact in two places, so a merge that dropped Team from either
would have trapped the user on the teams screen with the MORE tab dark.

Verified after resolving: solution builds with no errors and no new warnings,
the Android head builds, and every suite passes — App 214, Layout 73, Api 162,
Infrastructure 34, Contracts 25, Session 54. App gained the three shell-flow
tests main brought with it.

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

README.md

@@ -331,6 +331,12 @@ that design now; the desktop's own v2 is a 190-pixel labelled sidebar in place o
 search box in the titlebar, and session tabs as pills. Its light theme is not built — see
 [`docs/design-import-gaps.md`](docs/design-import-gaps.md) — so the application is dark on both.
 
+**A connected phone shows one bar and then the terminal.** The header, the session strip and the bottom
+bar are collapsed while a shell is up, and a single 52-pixel row replaces them: back on the left, the
+sessions as pills, and a `+` on the right offering the three connections this application can make — a
+shell, a host's files over SFTP, or a bucket. The system back gesture does what the arrow does, and lowers
+that menu first if it is open.
+
 Widening the sidebar moved the desktop window's minimum from `880x560` to `1016x574`, which leaves every
 screen exactly the width it was designed against.