[TexasCoding]

Closes #571

Changes (22.9.0, minor)

• communications.block_trade_proposals.cancel(id) → DELETE /communications/block-trade-proposals/{id} (204), sync + async.
• communications.block_trade_proposals.reject(id) → POST /communications/block-trade-proposals/{id}/reject (204, no body), sync + async.
• Perps MarginMarket.minimum_quantity (FixedPointCount, optional; spec-required → PERPS_EXCLUSIONS server_omits_despite_required).
• Specs synced (also: settlement market_result enum gains '' — SDK field is plain str, no change; Go x-enumNames hint, description text). _generated regenerated, no diff.
• Both endpoints registered in METHOD_ENDPOINT_MAP. Version bump + CHANGELOG + docs.

Blast radius (hand-written; GitNexus unavailable)

• kalshi/resources/communications.py: two new methods appended to BlockTradeProposalsResource / AsyncBlockTradeProposalsResource; reuse existing _delete / _post_void helpers (non-idempotent verbs, never retried). No existing method touched.
• kalshi/perps/models/markets.py: one new optional field with default None; existing payloads and constructors unaffected. Consumers: perps markets list/get, any model_dump output gains one key.
• Tests only otherwise. No public rename/removal → no migration note.

Gates

ruff ✅ · mypy ✅ · unit 5122 passed ✅ · strict contracts ✅ (see job log)