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/promptbox.go

@@ -0,0 +1,49 @@
+package agent
+
+import (
+	"log/slog"
+	"strings"
+	"unicode/utf8"
+
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/icon"
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/input"
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+type PromptBoxOptions struct {
+	Placeholder string
+	// Width is in dots, zero 240; Lines zero means 3.
+	Width, Lines int
+	Disabled     bool
+}
+
+type PromptBoxResult struct {
+	Element *ui.Element
+	Changed bool
+	// Cast is the prompt cast this frame, else empty.
+	Cast string
+}
+
+// PromptBox: Enter or CAST casts the prompt; Shift+Enter breaks lines.
+func PromptBox(c *ui.Context, text string, value *string, o PromptBoxOptions) PromptBoxResult {
+	k := pixel.K(c)
+	w, lines := pixel.Or("PromptBox Width", o.Width, 240), pixel.Or("PromptBox Lines", o.Lines, 3)
+	var res PromptBoxResult
+	res.Element = ui.Column(c).Gap(k.D(4)).AlignItems(ui.End).Children(func() {
+		f := input.TextArea(c, text, value, input.TextAreaOptions{Placeholder: o.Placeholder, Width: w, Lines: lines, Disabled: o.Disabled, EnterSends: true})
+		empty := strings.TrimSpace(*value) == ""
+		b := input.Button(c, k.Msg("cast"), input.ButtonOptions{Variant: input.Primary, Icon: icon.Sparkle, Disabled: o.Disabled || empty})
+		res.Changed = f.Changed
+		// Off or veiled, a key sent this frame casts nothing.
+		if (f.Submitted || b.Clicked) && !empty && !f.Input.IsDisabled() {
+			res.Cast, *value = *value, ""
+			// The cleared field shows next frame and keeps focus.
+			f.Input.Focus()
+			c.Invalidate()
+			slog.Debug("8bit: prompt cast", "label", text, "runes", utf8.RuneCountInString(res.Cast))
+		}
+	})
+	return res
+}