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.

icon/items.go

@@ -30,6 +30,19 @@ var (
 		.....ee.....
 		............
 		............`)
+	Crystal = pixel.MustSprite(`
+		.....ee.....
+		....e##e....
+		...e#l##e...
+		..e#l####e..
+		..e#l###se..
+		..e#l###se..
+		..e#l###se..
+		..e#l###se..
+		..e#l##sse..
+		...e#lsse...
+		....e#se....
+		.....ee.....`)
 	Potion = pixel.MustSprite(`
 		....eeee....
 		....eeee....