fix: sync smarkets spec with upstream API changes

[realfishsam]

Fixes #543
Fixes #544
Fixes #545
Fixes #527
Fixes #528

[realfishsam]

PR Review: VERIFIED

What This Does

Updates the vendored Smarkets OpenAPI spec to reflect upstream API changes: adds CFTC jurisdiction, CFTC regulatory metadata objects on events/markets/contracts, original_price field on bets, original_bets array on fullcover orders, and relaxes required fields (price and to_return removed from fullcover required list).

Blast Radius

• core/specs/smarkets/Smarkets.yaml -- vendored spec only
• Downstream: when api.ts files are regenerated from this spec, the Smarkets exchange will gain typed access to these new fields. Until then, the fields are passthrough.

No runtime code changes, no SDK changes, no OpenAPI (pmxt) spec changes.

Findings

1. The cftc metadata objects use additionalProperties: true (free-form object). This is pragmatic for an evolving upstream schema, but means the type system won't enforce the shape of CFTC metadata. Acceptable for a vendored spec.
2. Removing price and to_return from the fullcover order required list is a relaxation. This is backward-compatible for consumers but could mask missing data if the upstream starts omitting these.

No blocking findings.

PMXT Pipeline Check

• Field propagation: N/A -- vendored spec, not pmxt unified types
• OpenAPI sync: N/A -- this is the vendor spec, not openapi.yaml
• Type safety: N/A

Semver Impact

patch -- vendored spec sync, no breaking changes to pmxt API surface

Risk

The api.ts files generated from this spec are not regenerated in this PR. Until regeneration runs, the new fields are only in the YAML. CI should catch if the generated stubs drift.