Reconcile OpenAPI 3.30.0 spec drift (v15.0.0)

[TexasCoding]

Closes #515. Closes #517.

Reconciles nightly spec-drift against upstream OpenAPI 3.29.0 → 3.30.0 (paths 96 → 99; 109 → 116 operations) plus matching perps, Klear, and AsyncAPI updates. Ships as v15.0.0 because several response/WS payload constructors gained required fields (same constructor-breaking precedent as v13/v14).

Breaking

• Series.categories (list[str], required). The category filter on series.list() matches any entry. Live list callers are unaffected; tests/mocks that construct Series must pass categories.
• GetTargetBalanceAllocationResponse.resting_margin_reservation ("max" / "sum", required). The GET now echoes the reservation policy previously write-only on set_target_balance_allocation.
• Perps MarginMarket.underlying_multiplier (str, required) — underlying units per contract-size unit.
• WS QuoteCreatedPayload.rfq_creator_id and QuoteAcceptedPayload.rfq_creator_id (str, required). Live stream callers are unaffected.

Added

• FCM subtrader admin on client.fcm: list_subtraders() / create_subtrader(subtrader_suffix=...), blocked_categories / update_blocked_categories, event_contract_daily_cap / update_event_contract_daily_cap / delete_event_contract_daily_cap.
• Optional CreateRFQRequest.target_cost_excludes_fees (and the same field on RFQ / Quote responses).
• Optional min_ts= on historical.fills / fills_all / orders / orders_all.
• Optional MarginMarket.product_metadata.
• Klear estimate_maintenance_margin_metadata(asset_class=, date=), funding_estimate_by_asset_class(), funding_schedule(asset_class=).
• Perps WS UpdateSubscriptionAction.get_snapshot — request a fresh orderbook snapshot without changing the subscription. get_snapshot does not persist market_tickers onto the subscription.
• Optional id on orderbook snapshot envelopes (core + perps) when the snapshot is a get_snapshot reply.

Changed (non-breaking)

• Perps WS ListSubscriptionsResponse.id is optional (spec dropped it from required).
• OkMsg accepts optional index_ids / underlying_tickers on subscribed-indices / subscribed-underlyings acks.

Spec notes

• Core OpenAPI 3.30.0: 116 operations / 115 mapped. Still unimplemented on the core client: POST /portfolio/intra_exchange_instance_transfer.
• Perps OpenAPI: 48 operations.
• Perps SCM: 24 → 27 operations. Still unimplemented: GET /margin/large_trader_positions.
• AsyncAPI still 15 channels. 12 typed subscribe_* helpers.

Test plan

• uv run pytest tests/ --ignore=tests/integration -q — 4509 passed, 3 skipped
• uv run ruff check on changed files — clean
• uv run mypy kalshi/ — clean
• New endpoints registered in METHOD_ENDPOINT_MAP / PERPS_SCM_METHOD_ENDPOINT_MAP and BODY_MODEL_MAP

Notes for reviewers

• GitNexus pre-edit impact: MEDIUM on Series, CreateRFQRequest, MarginMarket, GetTargetBalanceAllocationResponse, QuoteCreatedPayload, UpdateSubscriptionAction; LOW on FcmResource / Klear MarginResource method additions. No HIGH/CRITICAL symbol-level warnings. detect_changes reports CRITICAL at the whole-diff level because this is a spec-wide reconcile (same class of change as v13/v14).
• Version bump is major solely for constructor-required fields; live list/stream callers are unaffected.