[simplex]: an operator page for limit orders

[dharjeezy]

Stacked on #1275.

The dashboard lost its curve editors when prices moved onto limit orders, and nothing replaced them. /api/limit-orders has been there from the start, but the only way to reach it was curl, so an operator could see which markets simplex watches and not what it was offering on any of them.

This adds a Limit orders page at /limit-orders, between Overview and Orders.

What it shows

One row per order, live ones first and closed ones under their own heading. Each row reads as the offer it is: 1,500,000 CNGN left at 1,500 CNGN per USDC, the token taken in, the chain it fills on, and how long is left on the clock.

Amounts are whole tokens throughout, never the orderbook's 1e18. The operator states 1000 and reads 1,000 back. fromScaled is the only place the scale is handled.

The badge answers "is this actually working", which the status column alone does not:

• open with a commitment is On the book.
• open with no commitment is Posting, because the row is live before the orderbook has answered.
• open carrying a lastError stays On the book but turns amber and shows the refusal, since the row stays open and the next cycle tries again.
• resizing is Resizing, a fill being settled.
• cancelled, expired, filled and rejected say so plainly.

What it does

Posting an order asks for the two amounts, in whole tokens, and shows the rate they imply before anything is sent. The operator chooses amounts, not a rate. It also asks which chain the order fills on and which sources it accepts, defaulting to every chain the filler watches, since an order that accepts none is one the orderbook refuses outright.

Opening an order shows what is left of it, what live bids are holding against it, and the fills that took the difference. That is what makes a shrunken remaining explicable rather than a number that quietly moved. It can be cancelled from there while it is still live.

The list reloads every ten seconds and after every mutation. A posting lands, expires or is filled without the operator doing anything, so the page cannot be a snapshot of the moment it opened.

Validation

ui:check, ui:build and pnpm build are clean. The package suite is 851 passing, with the same 19 failures every branch in this stack has: they need RPC endpoints, a loopback alias this machine lacks, or live testnets.

Ten unit tests cover the display logic that carries the reasoning: scaling, which leg is paid out, the rate string, available flooring at zero, each badge case, and the expiry clock.

Left out on purpose

The Markets page stays. A [[pairs]] entry no longer gates matching, but it still decides which strategies boot, so removing it is a separate decision.

The page polls rather than subscribing. The server already emits limit-order:posted and limit-order:rejected on the socket feed, so moving the list onto it is a straightforward follow-up.