WIP: Add multiplayer Snake game

N-player (2-8) real-time Snake game alongside Connect 4.
Lobby has tabs to switch between games. Players join via
invite link with 10-second countdown. Game loop runs at
tick-based intervals with NATS pub/sub for state sync.

Keyboard input not yet working (Datastar keydown binding
issue still under investigation).

ui/snakeboard.go

@@ -0,0 +1,92 @@
+package ui
+
+import (
+	"fmt"
+
+	"github.com/ryanhamamura/c4/snake"
+	"github.com/ryanhamamura/via/h"
+)
+
+func SnakeBoard(sg *snake.SnakeGame) h.H {
+	state := sg.State
+	if state == nil || sg.Status != snake.StatusInProgress && sg.Status != snake.StatusFinished {
+		return nil
+	}
+
+	// Build a lookup grid for rendering
+	type cellInfo struct {
+		snakeIdx int // -1 = empty, -2 = food
+		isHead   bool
+	}
+	grid := make([][]cellInfo, state.Height)
+	for y := 0; y < state.Height; y++ {
+		grid[y] = make([]cellInfo, state.Width)
+		for x := 0; x < state.Width; x++ {
+			grid[y][x] = cellInfo{snakeIdx: -1}
+		}
+	}
+
+	for fi := range state.Food {
+		f := state.Food[fi]
+		if f.X >= 0 && f.X < state.Width && f.Y >= 0 && f.Y < state.Height {
+			grid[f.Y][f.X] = cellInfo{snakeIdx: -2}
+		}
+	}
+
+	for si, s := range state.Snakes {
+		if s == nil {
+			continue
+		}
+		for bi, bp := range s.Body {
+			if bp.X >= 0 && bp.X < state.Width && bp.Y >= 0 && bp.Y < state.Height {
+				grid[bp.Y][bp.X] = cellInfo{snakeIdx: si, isHead: bi == 0}
+			}
+		}
+	}
+
+	// Cell size scales with grid dimensions
+	cellSize := 20
+	if state.Width <= 20 {
+		cellSize = 24
+	}
+
+	var rows []h.H
+	for y := 0; y < state.Height; y++ {
+		var cells []h.H
+		for x := 0; x < state.Width; x++ {
+			ci := grid[y][x]
+			class := "snake-cell"
+			style := fmt.Sprintf("width:%dpx;height:%dpx;", cellSize, cellSize)
+
+			switch {
+			case ci.snakeIdx == -2:
+				class += " snake-food"
+			case ci.snakeIdx >= 0:
+				s := state.Snakes[ci.snakeIdx]
+				colorIdx := ci.snakeIdx
+				if colorIdx < len(snake.SnakeColors) {
+					bg := snake.SnakeColors[colorIdx]
+					style += fmt.Sprintf("background:%s;", bg)
+				}
+				if !s.Alive {
+					class += " snake-dead"
+				}
+				if ci.isHead {
+					class += " snake-head"
+				}
+			}
+
+			cells = append(cells, h.Div(h.Class(class), h.Attr("style", style)))
+		}
+		rowAttrs := append([]h.H{h.Class("snake-row")}, cells...)
+		rows = append(rows, h.Div(rowAttrs...))
+	}
+
+	boardStyle := fmt.Sprintf("grid-template-columns:repeat(%d,1fr);", state.Width)
+	attrs := []h.H{
+		h.Class("snake-board"),
+		h.Attr("style", boardStyle),
+	}
+	attrs = append(attrs, rows...)
+	return h.Div(attrs...)
+}