Add a scorekeeper for games the app does not deal

A pencil, reachable from the main menu: say how many are playing, name
them, and write down what each scored every round. The tally sits at the
foot of the screen because that is the one number anybody looks up.

Points are recorded against a player's id rather than their position,
which is what lets the players be dragged into a different order without
their scores moving with them. Ids are never reused, so somebody sitting
down where somebody else got up starts at nought instead of inheriting a
stranger's score. Removing a player does take their points with them: a
score nobody can see is a score nobody can correct.

The drag leaves the sheet alone until the finger lifts. Rows move on
screen as the drag passes them, but the positions the gesture is working
from cannot shift underneath it, and the handlers read the sheet through
rememberUpdatedState so a drag cannot be applied to a stale copy and
throw away a name typed since.

Rounds are not written in ink — tapping one reopens it for correction or
strikes it out — and the sheet is saved as it is edited, so a phone call
does not lose the game. It lives in its own DataStore rather than with
the settings: a game in progress is not a preference.

score/ScoreSheet.kt has no Android in it, for the same reason game/ does
not, and every rule above is unit-tested on the JVM.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_019Pr6B8xDDtJJcb6WJMw7Ud

README.md

@@ -41,6 +41,32 @@ Each client is then sent a state **redacted for its own seat**, so opponents'
 hands and the deck order are never transmitted to devices that should not see
 them.
 
+## Scorekeeper
+
+**Scorekeeper** on the main menu is a pencil for games the app does not deal —
+darts, cribbage, whatever is actually on the table. Say how many are playing,
+name them, and write down what each of them scored every round; the running
+tally sits at the foot of the screen, where the one number anybody looks up is
+always visible.
+
+Players can be renamed, added, removed or **dragged into a different order** at
+any point in a game. That works because points are recorded against a player's
+id rather than their position, so reordering the sheet moves the columns and
+nothing else. Ids are handed out once and never reused: somebody sitting down
+where somebody else got up starts at nought instead of inheriting a stranger's
+score. Removing a player does take their points with them — a score nobody can
+see is a score nobody can correct.
+
+Rounds are not written in ink. Tapping one reopens it for correction or lets it
+be struck out, and the totals follow.
+
+The sheet is saved as it is edited, so leaving the app or taking a phone call
+does not lose the game. It is kept in its own DataStore rather than with the
+settings, because it is a game in progress rather than a preference.
+
+`score/ScoreSheet.kt` holds the whole model and, like `game/`, has no Android in
+it: every rule above is a pure function and unit-tested on the JVM.
+
 ## Settings
 
 - **Sound** on/off.
@@ -247,6 +273,7 @@ game/          rules engines and AI — pure Kotlin, no Android, unit-tested
   chess/       Chess model, FEN, move generation, search
   tayu/        Ta Yü tile geometry, river rules, scoring, AI
 net/           wire protocol, LAN transport, lobby, match driver
+score/         scorekeeper sheet — pure Kotlin, unit-tested — and its store
 settings/      DataStore-backed preferences
 update/        GitHub Releases OTA updater
 ui/            Compose screens