Start on the main screen

[benknoble]

This jumps us in to the action right away. To make this work, we need the following (§§ 3.1–3.7 of the current "How to Play" documentation as of b3bfb41 (server: unify formlet shorthands, 2024-06-28) plus items from transitions "to-play"):

• [x] set number of players via menu (via db3569f (gui: edit number of players via menu item, 2024-07-06))
• [x] edit players (max HP via 70e5917 (players: change max HP mid-scenario, 2024-06-14), names via 1f8b95b (gui/player-info: allow editing player names, 2024-06-28))
• [x] changing level via menu (via d2f7c11 (gui/manager: add ability to edit scenario level, 2024-06-19))
• [x] select bestiary via menu (via 3182ecb (allow selecting bestiary via menu, 2024-09-06))
• [ ] remove monster group (TBD: see 567511a (gui/manager: prototype edit monster groups, 2024-07-04))
• [x] setup loot deck via menu (via a9f75ce (add edit loot deck menu item, 2024-09-07))
• [x] adjust prompts via menu (via roughly bb41a59 (consolidate round prompt menu items, 2023-11-05))
• [x] shuffle modifier deck via menu (via #67)

Most of these required changes would improve the experience even without the main goal; for example, last night I needed to change a player's health before we got started, and it required completely restarting the app.

[benknoble]

• "Removing" Players is practically like killing them, something I've wanted for a minute anyway. Need to make sure that environment is appropriately adjusted: killing a player mid-scenario doesn't affect the C in formulas, but setting up fewer players does.
• This suggests the dual "remove monster group." Current formatting makes this less necessary, but it might improve performance?

[benknoble]

• Loot deck: cards that have already been looted can stay (but maybe we need a "Clear loot" button?); what about cards in the deck? Changing decks entirely should clear that (if not undoable, oh well?), but might also want to just move cards around… order? (Recall oddities from monster deck.)

[benknoble]

• bestiary: launch picker. If confirmed, remove all monster groups and ability decks; load new bestiary in the usual way.
• loot deck: launch picker. If confirmed, remove current deck (and all player loot?); load new deck as usual.