Add agent components 451-465 and icon.Crystal

Fifteen components that dress an AI agent's work as an RPG party:
AgentCard, ToolCall, PlanQuest, ThinkingOrb, TokenMana, ApprovalPrompt,
AgentLog, SubAgentParty, MemoryCrystals, AgentStatus, DiffScroll,
ModelSelect, PromptBox, CostCoins and Checkpoints.

The context window is HP and the token budget MP; tool calls are spells
that CAST, glow, then land OK or FAILED; the transcript reads as a battle
log whose newest line types itself out; models line up like fighters.
Busy signs keep moving under Reduce Motion, decoration stops. Commands
and prompts never reach the log, and a veiled PromptBox casts nothing.

icon.Crystal is the new 12x12 save and memory crystal.

agent/diffscroll.go

@@ -0,0 +1,121 @@
+package agent
+
+import (
+	"fmt"
+	"math"
+	"strconv"
+	"strings"
+
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+// FileDiff is a changed file: lines added and removed.
+type FileDiff struct {
+	Path           string
+	Added, Removed int
+}
+
+type DiffScrollOptions struct {
+	// Width is in dots; zero means 220.
+	Width int
+}
+
+// DiffScroll unrolls a parchment of changed files, lines counted.
+func DiffScroll(c *ui.Context, text string, files []FileDiff, o DiffScrollOptions) *ui.Element {
+	k := pixel.K(c)
+	if len(files) == 0 {
+		panic("agent: DiffScroll has no files")
+	}
+	add, del := 0, 0
+	said := make([]string, 0, len(files)+1)
+	for _, f := range files {
+		if f.Path == "" || f.Added < 0 || f.Removed < 0 || f.Added > math.MaxInt-add || f.Removed > math.MaxInt-del {
+			panic(fmt.Sprintf("agent: DiffScroll file %q +%d -%d", f.Path, f.Added, f.Removed))
+		}
+		add, del = add+f.Added, del+f.Removed
+		said = append(said, f.Path+" +"+strconv.Itoa(f.Added)+" -"+strconv.Itoa(f.Removed))
+	}
+	w := pixel.Or("DiffScroll Width", o.Width, 220)
+	total := fmt.Sprintf(k.Msg("files_changed"), len(files))
+	said = append(said, total+" +"+strconv.Itoa(add)+" -"+strconv.Itoa(del))
+	// Count columns fit the totals, the widest of them.
+	aw, dw := pixel.MicroWidth("+"+strconv.Itoa(add)), pixel.MicroWidth("-"+strconv.Itoa(del))
+	bx := w - 8 - 24
+	dx := bx - 6 - dw
+	ax := dx - 4 - aw
+	if ax-12 < 24 || pixel.Measure(total) > ax-12 {
+		panic(fmt.Sprintf("agent: DiffScroll Width %d is too narrow", w))
+	}
+	h := 6 + 4 + (len(files)+1)*pixel.LineHeight + 4 + 6
+	return ui.Box(c).Size(k.D(w), k.D(h)).Role(ui.RoleImage).Label(text).Description(strings.Join(said, "; ")).Draw(func(p *ui.Painter, r ui.Rect) {
+		g := k.Canvas(p, r)
+		g.Rect(4, 6, w-8, h-12, pixel.Lit)
+		g.VLine(4, 6, h-12, pixel.Shade)
+		g.VLine(w-5, 6, h-12, pixel.Shade)
+		rod(g, 0, w)
+		rod(g, h-6, w)
+		row := func(y int, name string, a, d int) {
+			g.Text(8, y, name, pixel.Ink, 1)
+			plus, minus := "+"+strconv.Itoa(a), "-"+strconv.Itoa(d)
+			g.Micro(ax+aw-pixel.MicroWidth(plus), y+6, plus, ink(a, pixel.Good), 1)
+			g.Micro(dx+dw-pixel.MicroWidth(minus), y+6, minus, ink(d, pixel.Bad), 1)
+			blocks(g, bx, y+6, a, d)
+		}
+		y := 10
+		for _, f := range files {
+			row(y, tail(f.Path, ax-12), f.Added, f.Removed)
+			y += pixel.LineHeight
+		}
+		g.Checker(8, y+1, w-16, 1, pixel.Shade)
+		row(y+4, total, add, del)
+	})
+}
+
+// ink is s for a count, Faint for none.
+func ink(n int, s pixel.Slot) pixel.Slot {
+	if n == 0 {
+		return pixel.Faint
+	}
+	return s
+}
+
+// rod is a scroll's wooden roller, capped past the paper.
+func rod(g pixel.Canvas, y, w int) {
+	g.Rect(1, y+1, w-2, 4, pixel.Shade)
+	g.HLine(1, y, w-2, pixel.Edge)
+	g.HLine(1, y+5, w-2, pixel.Edge)
+	g.Rect(0, y, 3, 6, pixel.Edge)
+	g.Rect(w-3, y, 3, 6, pixel.Edge)
+}
+
+// blocks shares five squares between added and removed.
+func blocks(g pixel.Canvas, x, y, a, d int) {
+	good := 0
+	if a > 0 || d > 0 {
+		good = int(math.Round(5 * float64(a) / (float64(a) + float64(d))))
+	}
+	for i := range 5 {
+		ink := pixel.Bad
+		switch {
+		case a == 0 && d == 0:
+			ink = pixel.Shade
+		case i < good:
+			ink = pixel.Good
+		}
+		g.Rect(x+i*5, y, 4, 4, ink)
+	}
+}
+
+// tail cuts s from the left, so the name shows.
+func tail(s string, width int) string {
+	if pixel.Measure(s) <= width {
+		return s
+	}
+	rs := []rune(s)
+	for len(rs) > 0 && pixel.Measure("…"+string(rs)) > width {
+		rs = rs[1:]
+	}
+	return "…" + string(rs)
+}