fix(ts-sdk): validate hosted limit order price

[realfishsam]

Summary

• Add TypeScript hosted buildOrder validation for limit-order price presence and positivity.
• Cover missing/zero limit prices with a regression test that verifies no hosted request is dispatched.

Fixes #1287

Test Plan

• npm test -- --runTestsByPath tests/hosted-dispatch.test.ts -t "positive price" --runInBand (pass; used local untracked generated/src stubs because this checkout cannot regenerate TypeScript OpenAPI output: java is unavailable)
• npm test -- --runTestsByPath tests/hosted-dispatch.test.ts --runInBand (blocked by pre-existing/local generated-stub limitations outside this change: fetchBalance empty stub response and NotSupported instanceof mismatch)
• npm run generate:sdk:typescript --workspace=pmxt-core (blocked locally: java: not found)
• git diff --check

[realfishsam]

CI note: the scoped TypeScript hosted price-validation change is covered by the targeted regression test, but generated-sync checks are currently red from unrelated repo-wide drift on main (Hunch exchange surfacing plus generated client/API reference diffs such as market_id/fee trade fields and source_exchange filters). I did not fold that broad drift into this focused fix PR.

Local checks run:

• npm test -- --runTestsByPath tests/hosted-dispatch.test.ts -t "positive price" --runInBand — PASS (with local untracked generated-client stubs because this checkout cannot regenerate OpenAPI output: java is unavailable)
• git diff --check — PASS

Blocked checks observed on GitHub:

• Verify exchanges reach all consumer SDKs — unrelated missing Hunch exports
• Verify client.ts/client.py/API_REFERENCE.md files are up-to-date — broad generated drift unrelated to SDK drift: Python hosted _hosted_build_order_request validates limit-order price presence and positivity; TypeScript _hostedBuildOrderBody does not #1287

[realfishsam]

PR Review: PASS (NOT VERIFIED)

What This Does

Adds client-side validation in the TypeScript hosted order build path so limit orders must include a positive price before dispatching to hosted PMXT.

Blast Radius

TypeScript SDK hosted trading helper _hostedBuildOrderBody and buildOrder/createOrder hosted dispatch validation. Core exchange execution, OpenAPI schemas, and Python SDK are not changed.

Consumer Verification

Before (base branch):
A hosted limit order with missing/zero/non-positive price could be serialized into the hosted build body and sent onward, leaving validation to the backend:

await api.buildOrder({ outcomeId, side: "buy", type: "limit", amount: 5 } as any)
// base: local body construction did not reject before fetch

After (PR branch):
Static review shows _hostedBuildOrderBody now rejects non-market orders unless Number(params.price) > 0, before to6dec and before any network dispatch:

if (orderType !== "market" && !(Number(params.price) > 0)) {
  throw new InvalidOrder("limit orders require a positive price");
}

The added test asserts buildOrder throws InvalidOrder and makes zero fetch calls for a limit order without a price.

Test Results

• Build: PASS (npm run build --workspace=pmxt-core)
• Unit tests: NOT VERIFIED. npx jest -c sdks/typescript/jest.config.cjs sdks/typescript/tests/hosted-dispatch.test.ts --runInBand failed before tests ran with sdks/typescript/pmxt/client.ts:15:8 - TS2307: Cannot find module '../generated/src/index.js'.
• Server starts: NOT RUN (local SDK pre-dispatch validation only)
• E2E smoke: NOT VERIFIED (no hosted credentials/back-end dispatch exercised)

Findings

No blocking findings.

PMXT Pipeline Check

• Field propagation (3-layer): N/A
• OpenAPI sync: N/A
• Financial precision: OK; no new price arithmetic, only positive-presence validation.
• Type safety: OK in changed path; full TS test compile blocked by missing generated imports.
• Auth safety: N/A

Semver Impact

patch -- client-side validation fix for an invalid limit-order path.

Risk

This intentionally rejects price=0; that is consistent with limit-order semantics here, but I did not verify hosted backend behavior end-to-end because tests could not run past missing generated artifacts.