Characters: campaigns, "Spielen" main menu, story unlocks

- One world per campaign and difficulty in a character file (sections
  ancaria<d> / underworld<d>; old world<d> renamed when read). Difficulty
  unlocks by the shared hero's story completions (hero header +0xed..),
  shared by both campaigns.
- Main menu: "Kampagne Ancaria", "Kampagne Underworld" and "Spielstaende"
  become "Spielen" (mods/mainmenu.cpp). The load window lists all
  characters, the world dialog offers both campaigns, "Neuer Charakter"
  asks for the campaign and opens character creation.
- Character window: no Underworld import mode (new Underworld heroes, all
  classes, slots light up), no "Importieren"; load window without
  "Speichern".

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/characters.md

@@ -78,8 +78,11 @@ Decided (2026-10-19, follow-up):
   0x425160) +0x5704, one byte counter per difficulty (6 entries).
   `0x424bc0` (k) increments, `0x424be0` (k) reads, `0x424c00` (k, value) sets.
   The script opcode at 0x4aed26 increments counter[`g_gameLevel`]: the story
-  end. The counters travel in the save header (loader 0x61bb19..) and in the
-  hero file (loadHero 0x606632.., saveHero 0x60444c..). The console cheats
+  end. The counters travel in the save header (dwords at +0x88.., loader
+  0x61bb19..) and in the hero header chunk 0xc3 (bytes at +0xed.., written by
+  0x604360, read by loadHero 0x606632..; +0xec is `g_gameLevel`). Checked in
+  a character file (2026-10-20): Silber and Gold completed, played on Platin =
+  [0, 1, 1, 0, 0] in the hero and the Platin world. The console cheats
   `bronze` / `silber` / ... (0x615d00..) increment them too.
 - Vanilla offers a difficulty by **hero level**, not by completion:
   thresholds `0xad2dc4..0xad2dd4` (5 dwords, parsed from the balance data key
@@ -123,6 +126,28 @@ Decided (2026-10-19, follow-up):
   without a world starts a new game with the shared hero.
 - The save key and the Esc menu ("Spielstände" becomes "Speichern") save
   directly, without the save window.
+- Main menu: "Kampagne Ancaria", "Kampagne Underworld" and "Spielstände"
+  become one "Spielen": the characters, loaded or started in either campaign
+  on any difficulty; new characters from there too. A character file holds a
+  world per campaign and difficulty; the format must take more difficulties
+  later. Decided: no level requirement for the Underworld (vanilla: hero level
+  25, 0x70c48b), story completions open the next difficulty in both campaigns,
+  "Neuer Charakter" is a button in the Spielen window.
+
+### Campaigns (measured / read 2026-10-20)
+
+- `g_campaign` 0x182cdc8 (u16): 0 Ancaria, 1 Underworld. The main menu's
+  event handler (0x711fa0) sets it by entry name before an entry handles an
+  event (UI_LABEL_NEWGAME 0, UI_LABEL_NEWADDON 1); both entries show
+  UI_CHARACTER. `cEngine::Save` writes it to the save header +0x24 (2
+  Ancaria, 3 Underworld, 0x61a5c5), `cEngine::Load` sets it from there
+  (0x61bafd). The load window lists only saves of the running campaign
+  (0x71e2b9).
+- Story completions are counted per difficulty only (the same counter for
+  both campaigns).
+- Main menu (cUI_MainMenu, entries built by 0x712f30): cUI_StaticText64FX
+  entries (constructor 0x753d70), name +0x30, rect +0x24 (0x20 apart), text
+  id +0x78, command +0x88; main page vector +0x158, children +0x90.
 
 ## Implementation (`src/mods/characters.cpp`, `charfile.{h,cpp}`)
 
@@ -130,24 +155,64 @@ Decided (2026-10-19, follow-up):
 
 - `Documents\Sacred\save\characters\CharacterNN.sacredK`: "SKCH", version 1,
   section count, then `{name[16], offset, size}` entries. Sections: `meta`
-  (JSON: format, name UTF-8, class, level, lastDifficulty, migratedFrom,
-  heroFrom), `hero` (AMH as `cEngine::SaveHero` writes it), `world<d>` (AMS as
-  `cEngine::Save` writes it). Written to a temp file, then moved over.
-- `CharacterNN.autosave.sacredK`: same layout, one world (`meta.difficulty`).
+  (JSON: format, name UTF-8, class, level, lastCampaign, lastDifficulty,
+  migratedFrom, heroFrom, heroFromCampaign), `hero` (AMH as
+  `cEngine::SaveHero` writes it), one world per campaign and difficulty,
+  `ancaria<d>` / `underworld<d>` with d = `g_gameLevel` (AMS as
+  `cEngine::Save` writes it). Sections are named, not slotted: a higher
+  difficulty (or another campaign) is one more section. Files of the first
+  format named Ancaria's worlds `world<d>`; they are renamed when read
+  (charfile.cpp) and written under the new name at the next save. Written to
+  a temp file, then moved over.
+- `CharacterNN.autosave.sacredK`: same layout, one world (`meta.campaign`,
+  `meta.difficulty`).
 - The game's save folder is redirected to `characters\_work` (userfolders);
   the game reads and writes `world.PAK` / `hero.pax` there.
 - Deleted characters move to `characters\deleted\`.
 
+### Main menu (`src/mods/mainmenu.cpp`)
+
+After the build (0x712f30) the NEWGAME and NEWADDON entries are removed (out
+of both vectors, deleted) and UI_LABEL_LOADGAME ("Spielstände", shows
+UI_WND_SAVEGAME) moves to the top with the text "Spielen"; the others move up,
+keeping the gap before "Beenden".
+
 ### Load window (cUI_Savegame)
 
 - Before each scan (0x71e330) one preview `GAMEnn.PAK` per character is
   written into `_work` (header, thumbnail, world time, description
-  "Name - Klasse"); row nn = character nn. The row's second line (call
-  0x71db2a to SetText 0x736f00) shows "Stufe N - difficulty".
-- Laden (action 4 / 0xb) opens the difficulty dialog when there is more than
-  one choice: worlds, newer autosaves "(Autosave)", and "(neu)" for every
-  difficulty up to max(highest world, Silber) without a world (needs the
-  shared hero; not in multiplayer, byte 0x182cb6c).
+  "Name - Klasse"); row nn = character nn. The preview's campaign field is
+  the running campaign, so the window lists every character. The row's
+  second line (call 0x71db2a to SetText 0x736f00) shows
+  "Stufe N - Campaign - difficulty".
+- Laden (action 4 / 0xb) opens the world dialog when there is more than one
+  choice: per campaign worlds, newer autosaves "(Autosave)", and "(neu)" for
+  every difficulty without a world up to the highest open one (needs the
+  shared hero; not in multiplayer, byte 0x182cb6c). Open: Bronze and Silber,
+  every difficulty up to the highest with a world in either campaign, and the
+  one after each difficulty whose story the shared hero completed (hero
+  header +0xed..). `g_campaign` is set to the chosen world's before loading
+  or starting.
+- "Neuer Charakter" (two places below Löschen; main menu only) asks for the
+  campaign, sets `g_campaign`, hides the window and shows UI_CHARACTER (the
+  game's character creation, as the main menu's campaign entries did). The
+  first save makes the character file.
+- Vanilla made no new heroes for the Underworld: `cUI_Character::Show`
+  (vf24 0x70e2a0) switches to mode 7 in single player with `g_campaign` 1
+  (0x70e3e8), the import of an exported hero of level 25+ (0x70eedc); with no
+  exported heroes its slots were empty, and slots below level 25 never lit
+  up (render 0x70f4df / 0x70f57c) (reported 2026-10-20). All eight campaign
+  checks of the window (0x70c473, 0x70d199, 0x70e3e8, 0x70eade, 0x70eeb2,
+  0x70f4df, 0x70f57c, 0x70f6aa) read a constant Ancaria instead: creation
+  with all classes in both campaigns; the start (ExecuteAction 0x70d0f0,
+  action 1) uses `g_campaign` as set.
+- Class selection without "Importieren" (request 2026-10-20): button +0x3a0
+  (caption UI_IMPORT in modes 0/1); its modes-0/1 draw (0x70f67e) is removed,
+  its click (0x70eab4 / 0x70eac7, SetMode(7)) jumps to the handler's end.
+- Load window without "Speichern" (request 2026-10-20; saving is direct):
+  button +0x820 (action 1, disabled in load mode, so its click falls through)
+  is not drawn (jump over 0x71ddbc); Löschen (+0x8dc) takes its rect, our
+  buttons follow below it.
 - "Umbenennen" (below Löschen; not for the character being played) asks for
   a name; keys go to the field through the input key capture. The name is
   only in the hero header chunk 0xc3 (+8, UTF-16, 0x40 chars): rewritten in
@@ -202,7 +267,6 @@ kept, the newest file overall is the shared hero.
 
 ## Open
 
-- Unlocking by story completion (counters at save header +0x88..).
 - Reset a difficulty.
 - Remove the export / import UI.
 - Silent autosave every 10 minutes.