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/thinkingorb.go

@@ -0,0 +1,67 @@
+package agent
+
+import (
+	"math"
+
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+type ThinkingOrbOptions struct{}
+
+var (
+	// Swirl arms run Lit at the heart, Info, then Magic.
+	swirl = []pixel.Slot{pixel.Lit, pixel.Info, pixel.Magic}
+	// mist is the glow's half width, row by row.
+	mist = func() map[int]int {
+		half := map[int]int{}
+		for _, d := range ring(15) {
+			half[d[1]] = max(half[d[1]], abs(d[0]))
+		}
+		return half
+	}()
+)
+
+// ThinkingOrb is a crystal ball that swirls while thinking.
+func ThinkingOrb(c *ui.Context, text string, thinking bool, o ThinkingOrbOptions) *ui.Element {
+	k := pixel.K(c)
+	word := k.Msg("idle")
+	if thinking {
+		word = k.Msg("thinking")
+	}
+	return ui.Box(c).Size(k.D(44), k.D(48)).Role(ui.RoleStatus).Label(text).Description(word).Draw(func(p *ui.Painter, r ui.Rect) {
+		g := k.Canvas(p, r)
+		g.Disc(22, 20, 19, pixel.Well)
+		// A busy sign: it swirls on under Reduce Motion.
+		if thinking {
+			for y, h := range mist {
+				g.Veil(22-h, 20+y, 2*h+1, 1, pixel.Magic, 4)
+			}
+			turn := float64(g.Busy(8)%12) * math.Pi / 6
+			for arm := range 3 {
+				px, py := 22, 20
+				for i := 1; i <= 16; i++ {
+					t := float64(i)*0.38 + turn + float64(arm)*2*math.Pi/3
+					x, y := 22+int(math.Round(float64(i)*math.Cos(t))), 20+int(math.Round(float64(i)*math.Sin(t)))
+					g.Line(px, py, x, y, swirl[(i-1)*3/16])
+					px, py = x, y
+				}
+			}
+			g.Disc(22, 20, 2, pixel.Lit)
+		}
+		g.Circle(22, 20, 19, pixel.Edge)
+		g.Rect(11, 8, 4, 2, pixel.Lit)
+		g.Rect(10, 10, 2, 2, pixel.Lit)
+		g.Rect(13, 38, 18, 3, pixel.Edge)
+		g.Rect(8, 41, 28, 6, pixel.Shade)
+		g.HLine(8, 41, 28, pixel.Edge)
+	})
+}
+
+func abs(n int) int {
+	if n < 0 {
+		return -n
+	}
+	return n
+}