Describe the fullscreen game view (#267)

Concepts gets a Fullscreen section and a sentence under Release. Architecture lists fullscreen.ts and FullscreenCorner.ts. Development has the new e2e module 61 and the sum of 1580 checks.

Architecture.md

@@ -124,6 +124,8 @@ src/viewport/          WorldViewport (the drawing of a world or a holder, the ba
                        a `ViewSource` — the project and word of a change — so a released game draws without the
                        editor, #266), gamePointer (the mouse handed to a running world), projectFiles (the file
                        libraries pointed at the server, and what a project names fetched ahead),
+                       fullscreen + FullscreenCorner (the browser's Fullscreen API, when the corner button shows,
+                       and the button itself, shared by the Game tab and the released game, #267),
                        view (transforms), items (what to draw), symbols (how to draw it),
                        symbolIcons (the SVG files in icons/, parsed once, in the theme's colours, #175),
                        FileLibrary (load once, never retry a failure, tell the listeners) ← TextureLibrary, FontLibrary;

Concepts.md

@@ -71,6 +71,13 @@ Fixed steps start on a whole screen pixel, so pixel art at 100% stays sharp. The
 pixel, and Fit then names the factor in screen pixels (`Fit · 156%`). The choice is saved with
 the project, like *Play starts*, but it is no undo step: Ctrl+Z undoes edits, not a look at the game.
 
+**Fullscreen** (#267). The button at the right end of the Game tab's header puts the game view on
+its own into fullscreen: no toolbar, no panels, no tab header, no console, at the scale the picker
+holds. A run goes on as before and the keys still go to the game. A button in the top right corner
+leaves fullscreen, and so does Esc, the browser's own key; the view is back in its tab as it was.
+Over a running game that corner button steps aside once the mouse has rested for 2 s and comes back
+with the next move. Stopping the run ends fullscreen too, since Stop goes back to the Scene tab.
+
 **While playing** (#265). How closely the editor follows a running game is one preset in
 *Menu → Project settings…*. The game itself runs every frame in each of them, and so does the
 picture of it on screen; only the panels are held back. With hundreds of objects spawning and
@@ -119,7 +126,8 @@ sound before one, and the keyboard would have nowhere to go. Every key belongs t
 included. A game that stops itself (`Stop game`) offers to play again; `Restart game` and
 `Load scene` work as in the editor. Persistent variables are saved in the player's browser under
 the link, apart from the editor's own saves. Plugins are not loaded on the link; the dialog warns
-when the project uses any, and when it has no scene to play.
+when the project uses any, and when it has no scene to play. The page has the same fullscreen button
+as the Game tab in its top right corner (#267); a click on it never reaches the game.
 
 **Toolbar and panels.** The toolbar carries five **icon buttons** and no captions (#183): the
 **menu** (three bars) on the left with *New project*, *Open project…*, *Snapshots…*, *Release…* and *Project settings…*,

Development.md

@@ -16,7 +16,7 @@ php tools/make-user.php <name> <password> [admin|user]        # an account; ever
 php tests/php/accounts.test.php                               # the API's account rules, no server needed (CI's gate job)
 php tests/php/snapshots.test.php                              # the snapshot store (#231), the same way
 php tests/php/releases.test.php                               # the release store (#266), the same way
-node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1574 editor checks, screenshots in /tmp/gm-e2e-*.png
+node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1580 editor checks, screenshots in /tmp/gm-e2e-*.png
 GM_STEPS=20 node tools/e2e.mjs                                # or 1-12, or 6,20 — a subset while working on one step
 ./e2e.sh start [GM_STEPS]                                     # the same run detached, see below
 ./e2e.sh status                                               # live progress, or the last run's result