Agent B: flat $10 large-cart discount

[RollNuts]

Adds a flat $10 large-cart discount in the SAME discount section of orders/pricing.py as PR #13. Standalone python -m pytest -q → 7 passed. Part of the canonical open collision pair with #13 — both touch the same lines in calculate_total; Veripsa signals which lands first (the roles can swap as the pair is re-analyzed).

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[veripsa-core]

Veripsa — heading to main

⏸ Wait in line — a direct collision is ahead

⏸ Veripsa paused this — you are in a real coupling with other in-flight work. To proceed, add the veripsa-ack label (an agent can run gh pr edit --add-label veripsa-ack; a human can click it), or wait for the other PR(s) to land and this clears automatically. Adding the label records your acknowledgement — not an approval or a pardon.

This PR reserves: orders/pricing.py, tests/test_pricing.py

Land in order. You collide in calculate_total (in orders/pricing.py) — that's the same code, not just the same file. You are queued behind GH-RollNuts PR-13. Landing in this order means you rebase onto their change once — not redo work after both land out of order. When the change ahead lands or withdraws, your reservation advances; if it withdraws, this clears.

⏳ A small rebase may also be needed in orders/pricing.py near line 22 — the overlap above is likely to surface as a textual merge conflict on rebase, which landing in order avoids. (Content-free heuristic — "likely", not certain.)

Overlapping PRs — 2 open PRs touch this same area. Suggested order to land them (most foundational first, so the others only revise once):

1. GH-RollNuts PR-13
2. GH-RollNuts PR-14 ← this PR

_{Veripsa records what is heading to main and who reserved what — it does not assert correctness. Advisory by default; your branch-protection policy decides what blocks.}