docs(ui): sync docs to the app-shell; fix stale nav comments

Rewrite ui/docs (navigation, order-composer, auth-flow, pwa-strategy,
game-state + secondary topic docs) and ui/README for the single-URL
app-shell (in-memory screens/views, Back→lobby via shallow routing,
sessionStorage restore + validation, return-to-lobby). ui/PLAN.md gets a
Phase-10 supersede note (implemented; standalone-compatible). Fix stale
code comments (session-store auth gate, report-sections spec contract).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ui/docs/lobby.md

@@ -15,8 +15,8 @@ width.
 
 | Section              | Empty state           | Source                     | Action                                                    |
 | -------------------- | --------------------- | -------------------------- | --------------------------------------------------------- |
-| `create new game`    | (always visible)      | —                          | Navigates to `/lobby/create`                              |
-| `my games`           | `no games yet`        | `lobby.my.games.list`      | Click → `/games/:id/map`                                  |
+| `create new game`    | (always visible)      | —                          | Opens the create screen (`appScreen.go("lobby-create")`)  |
+| `my games`           | `no games yet`        | `lobby.my.games.list`      | Click → enters the game on the map view (`activeView.reset()` + `appScreen.go("game", { gameId })`) |
 | `pending invitations`| `no invitations`      | `lobby.my.invites.list`    | Accept (`lobby.invite.redeem`) / Decline (`lobby.invite.decline`) |
 | `my applications`    | `no applications`     | `lobby.my.applications.list` | Status badge (`pending` / `approved` / `rejected`)      |
 | `public games`       | `no public games`     | `lobby.public.games.list`  | Submit application via inline race-name form (`lobby.application.submit`) |
@@ -85,9 +85,10 @@ public game (FUNCTIONAL.md §3.3). Fields:
 | `start_gap_players`   | Advanced toggle  | `2`     |                                                        |
 | `target_engine_version` | Advanced toggle | `v1`   | Falls back to `v1` if blank                           |
 
-On success the page navigates back to `/lobby` and the new game shows
-up in `my games` once the lobby's onMount has had a chance to refresh
-the list.
+On success the create screen returns to the lobby
+(`appScreen.go("lobby")`) and the new game shows up in `my games`
+once the lobby's onMount has had a chance to refresh the list (the
+lobby screen remounts on return, so its onMount re-fires).
 
 ## Errors