test(cluster-tool): carry uwreqs.target_amount in the swap-scenario fixture (companion to wire-sysio#550)

[heifner]

Companion to wire-sysio#550, opened now so it is reviewed ahead of the regen rather than racing it.

⚠️ Do not merge yet — this is red by construction until the sysio.uwrit regen lands in wire-libraries-ts. That is the point of opening it early; see Sequencing.

What and why

#550 adds one additive field to the uw_request_t row — target_amount: uint64, the caller's original destination amount, retained as the fixed reference the race-time slippage check anchors on:

                     "name": "dst_amount",
                     "type": "uint64"
                 },
+                {
+                    "name": "target_amount",
+                    "type": "uint64"
+                },

uwreqRow() in SwapScenarioContext.test.ts returns the full SysioUwritUwRequestTType rather than a Partial, so the moment the regenerated types carry target_amount as required, the fixture stops compiling — which fails pnpm build (tsconfig.cjs.jest.json is a project reference) and the e2e gate behind it. One line fixes it.

That fixture is the entire surface

I checked every SysioUwritUwRequestTType reference in the repo. All the others are read positions — Promise<…> returns in five flow scenarios (flow-swap-private-reserves, flow-swap-to-wire, flow-reserve-lifecycle, flow-underwriter-slashing, SwapScenarioContext), a predicate parameter, a type alias in flow-swap-non-native-tokens, an array field in this same test. None constructs a row; an additive field cannot break any of them.

Live flow reads are unaffected regardless of merge order. They go through .tables.uwreqs.query() → get_table_rows, where nodeop serializes against the on-chain ABI and returns JSON, so the extra field simply arrives and is ignored by name-based reads. There is no host-side binary decoder to misalign either — the underwriter plugin reaches uwreqs over the same JSON-RPC path, not a hand-rolled struct. So the mid-struct insertion, which would matter for a raw binary decode, does not bite.

Sequencing

Verified against today's sdk-core, this errors:

packages/cluster-tool/tests/flow/contexts/SwapScenarioContext.test.ts(65,5): error TS2353:
Object literal may only specify known properties, and 'target_amount' does not exist
in type 'SysioUwritUwRequestTType'.

sdk-core is currently ahead of wire-sysio master and already carries #549's sysio.chalg types, so regenerating today would delete them. Order:

1. wire-sysio #549 merges
2. regenerate SysioContractTypes once
3. the wire-libraries-ts regen PR
4. this PR — in the same window as step 3, not after, or the gate is red in the gap

This is the same shape as the challenge_id fixture update riding #56 for the #549 regen — one cycle later, for #550.