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/testing.md

@@ -128,9 +128,10 @@ report" affordance (`import.meta.env.DEV`). The flow is:
 
 2. Run the UI dev server (`pnpm -C ui/frontend dev`), open the lobby,
    and use the "Load JSON…" file picker in the **Synthetic test
-   reports (DEV)** section. The page navigates to
-   `/games/synthetic-<uuid>/map` with the report wired into the
-   in-game shell.
+   reports (DEV)** section. The lobby enters a `synthetic-<uuid>` game
+   on the map view (`activeView.reset()` + `appScreen.go("game", {
+   gameId })`) with the report wired into the in-game shell. The
+   app-shell URL stays `/game/` — see [`navigation.md`](navigation.md).
 
 In synthetic mode:
 
@@ -139,16 +140,16 @@ In synthetic mode:
 - Composing orders works locally (overlay applies through
   `applyOrderOverlay` as usual), but **nothing is sent to the
   gateway** — `OrderDraftStore.scheduleSync` short-circuits because
-  the synthetic id is not a UUID and the layout deliberately does
-  not bind a `GalaxyClient` for this game.
+  the synthetic id is not a UUID and the in-game shell deliberately
+  does not bind a `GalaxyClient` for this game.
 - The order draft is persisted into the platform `Cache` under the
   same `order-drafts` namespace as real games, keyed by the
   synthetic id, so navigating back into the same synthetic session
   restores the draft. The cache is cleared with
   `__galaxyDebug.clearOrderDraft(gameId)` (DEV debug surface).
-- A page reload loses the in-memory report registry; opening the
-  same synthetic id afterwards redirects to /lobby. Re-load the JSON
-  to reseed.
+- A page reload loses the in-memory report registry; a restored
+  synthetic game whose report is gone falls back to the lobby
+  (`appScreen.go("lobby")`). Re-load the JSON to reseed.
 
 The synthetic-report parity rule requires every change that extends
 `decodeReport` to also extend the legacy parser in lockstep, or to