Limit orders display base-unit amounts for sub-dollar tokens

[premiumjibles]

Problem

When placing limit orders for sub-dollar tokens (e.g. ARB → USDC), SellAmount shows a massive base-unit number like "230,000,000,000..." instead of human-readable amounts. Users could sign orders with wildly wrong amounts.

tk ticket: sa-lhbw
Repro: Place a limit order for ARB → USDC (or any sub-dollar token).

Root Cause

Server-side code is structurally correct (summary.sellAsset.amount uses human-readable values). The bug is most likely an LLM reasoning error for sub-dollar tokens where:

1. LLM passes base-unit value as sellAmount after seeing precision: 18
2. orderParams.sellAmount (base unit) leaks into LLM's text response
3. LLM inverts limitPrice for sub-dollar tokens, producing enormous numbers

Fix

1. Input validation — reject sellAmount with >15 digits (defense in depth)
2. Sanity check — validate sellAmount * limitPrice vs market price (>1000x = error)
3. Schema description — explicit base-unit warning with sub-dollar token examples
4. Reduce leakage — filter orderParams from LLM-visible output
5. Apply to all tools — same fixes for createStopLoss.ts and createTwap.ts

Key Files

• apps/agentic-server/src/tools/limitOrder/createLimitOrder.ts
• apps/agentic-server/src/tools/stopLoss/createStopLoss.ts
• apps/agentic-server/src/tools/twap/createTwap.ts
• apps/agentic-server/src/routes/chat.ts

Acceptance Criteria

• Input validation rejects >15 digit sellAmount values
• Sanity check on sellAmount * limitPrice vs market price
• Schema descriptions warn about base-unit vs human-readable
• Manual test: ARB → USDC limit order shows correct amounts