[realfishsam]

Fixes #443

[realfishsam]

PR Review: VERIFIED

What This Does

Removes the deprecated mututals_description field from the Kalshi raw event interface, normalizer, and test fixtures. The event description now always falls back to deriveEventDescription() which synthesizes a description from the constituent market rules.

Blast Radius

• Kalshi exchange: fetcher.ts (raw type), normalizer.ts (mapping logic)
• Tests: exchange-normalizers.test.ts (fixture and assertion updated)
• No unified type, OpenAPI, or SDK changes

Findings

No blocking findings. The change is clean and well-scoped:

• Removes a field that was misspelled in the original Kalshi API (mututals vs mutuals), suggesting it was indeed deprecated/removed upstream.
• Test is updated to verify the fallback path, confirming deriveEventDescription produces a coherent result from market rules.
• No other code references mututals_description outside these files.

PMXT Pipeline Check

• Field propagation: OK (removal only affects raw type, unified description still populated via fallback)
• OpenAPI sync: OK (no BaseExchange.ts change)
• Type safety: OK

Semver Impact

patch -- removes usage of a deprecated upstream field, no API contract change

Risk

• If the Kalshi API still returns mututals_description on some events (i.e., not fully deprecated), those descriptions will now be silently ignored in favor of the derived description. This is acceptable since the derived description is the canonical fallback, but verify against live Kalshi responses.