Fix extended-hours orders: market_hours must match extended_hours

[mdicarlo-scaled]

Problem

Stock orders always send "market_hours": "regular_hours" in the order payload, even when --extended-hours is set. The Robinhood order API rejects the contradictory combination:

400 {"non_field_errors":["Extended hours and market hours mismatch."]}

so every --extended-hours order fails with BROKER_REJECTED.

Repro:

TOKEN=$(rhx --json live on --yes | jq -r '.data.live_confirm_token')
rhx --json orders stock place --symbol NG --side buy --type limit \
  --limit-price 4.50 --qty 1 --extended-hours --time-in-force gfd \
  --live-confirm-token "$TOKEN"
# -> BROKER_REJECTED: Extended hours and market hours mismatch.

Fix

Set market_hours to "extended_hours" when intent.ExtendedHours is true (payload construction in pkg/rhx/brokerage_orders.go).

Verification

• go test ./... passes.
• Verified against the live API: the exact order above (previously rejected) is accepted with this change (state: unconfirmed), and behaves normally through cancel.

🤖 Generated with Claude Code

[finlayi]

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