fix: repair the negotiation system (pricing, wallet guard, stable NPC) + one-shot-per-car rule

[wpinrui]

Description rewritten 2026-07-13. The original description advertised three cosmetic fixes. The branch is 15 commits and contains a negotiation pricing overhaul, a gameplay rule change, and a debug panel — none of which were mentioned. What follows is an honest account of the whole branch. Review against this, not the old text.

What this PR actually is

This is the repair for the negotiation system, which is currently shipped and broken on main in both directions at once — you can buy cars you cannot afford (going to negative money) and be silently overcharged on Accept. It is not a polish PR.

Scope: 15 commits, 19 files, src/ only. No data, config, or docs touched.

Bugs on main that this fixes

#	Bug on main	Fix here
1	No wallet guard. closeNegotiation deducted the price with no affordability check — you could buy a car you couldn't afford and go to negative money.	Affordability checks in submitOffer, acceptAtListPrice, and closeNegotiation, each raising a "You can't afford this." toast. The Accept button is also disabled when the player can't cover the asking price.
2	The asking price is a lie. The browse card showed listing.askingPrice; the modal labelled npc.targetPrice as "Asking price". These are unrelated numbers (targetPrice was market value × ~1.15). The player was quoted two different prices for the same car.	NPC pricing is re-anchored to listing.askingPrice. calculateNpcPricing() now takes an anchorPrice, and NegotiationItem carries askingPrice.
3	The Accept button charged the wrong amount. The button read Accept $<last counter> but acceptListPrice() charged npc.targetPrice — always higher. Silent overcharge.	Both the label and the charge now use item.askingPrice.
4	Trait badges rendered raw IDs — impatient instead of Impatient.	Uses getTraitDefinition(traitId).name.
5	NPC regenerated on every open. RNG was seeded on action count, so re-opening the same listing produced a different seller with different traits and prices.	Listing-ID hash seed → stable NPC per car.

⚠️ Gameplay rule change: "one shot per car"

This is new, it is not a bug fix, and it was not in the original description.

closeNegotiation now removes the listing from the market whenever the negotiation ends in anything other than an accepted sale (store/index.ts). Because Walk Away is wired directly to closeNegotiation, this means:

• Walking away from a haggle permanently destroys that listing.
• The NPC walking away on you permanently destroys that listing.

You get one negotiation per car, ever. This is a real design decision that deserves a real decision — flagging it loudly rather than letting it merge as an implementation detail.

⚠️ Debug panel included

DebugPanel.tsx / .css ship in this branch: an on-screen money setter, plus a debugSetMoney store action. It is gated on const DEBUG_MODE = true — hardcoded in store/index.ts, not import.meta.env.DEV — so it renders in a production build as written.

The owner has seen this and chosen to keep it. Noted here so nobody merges it by accident.

Pricing overhaul detail

The load-bearing change; everything else in negotiation sits on top of it.

• targetMultiplier base 1.15 → 1.0 — the NPC now targets the asking price rather than a markup over market value.
• walkAwayPrice is clamped to at most 90% of the anchor: min(anchor × walkAwayMultiplier, anchor × 0.90). Base walkAwayMultiplier is still 0.80 and traits still move it; the clamp is an upper bound only, guaranteeing at least a 10% negotiation band on every car.
• marketValue is still carried on NegotiationItem but no longer drives pricing.

UI polish

• Toasts moved to bottom-centre with a slide-up animation.
• Modal overlay opacity 0.6 → 0.25 across all five modals (two commits: 0.6 → 0.4, then → 0.25).
• Scroll-container bottom-padding collapse fixed via ::after spacer (Newspaper, Browse Results).
• Low-DPI map cards: removed overflow: hidden from .loc, border-radius moved onto the photo, responsive grid minimum min(390px, 100%), min-height: 0 on .map-body.

Closes #52.

Notes for the reviewer

• traitVisibilityPerPoint is net-zero here. One commit raised it 0.01 → 0.10, a later commit reverted it. No data file is touched. Don't chase it through the commit list — the balance question is being ticketed separately.
• A local two-dot diff (git diff main..) will show spurious .claude/ deletions. The branch predates PR chore: track .claude agent config in git #63; it never touched those files. A three-dot diff (git diff main...) — which is what GitHub's Files-changed tab shows — confirms src/-only, 19 files.

Known gaps this does not close

Real, on main, and out of scope — do not block on them, they have their own tickets:

• You still cannot accept an NPC's counter-offer. Accept takes the asking price; counters descend below asking, so accepting is always worse than the seller's own latest offer. The workaround is to retype the counter as your own bid.
• Cars can never be refuelled, so no car can ever be driven.
• Fitness has no effect on labor earnings or rest efficiency.
• negotiate_junker_purchase is a permanently dead activity card.

Test plan

Money path — the two financial bugs:

• Try to buy a car you cannot afford (exact money, slightly under, well under) — purchase is blocked with a "You can't afford this." toast, and money never goes negative.
• "Accept $X" is disabled with a tooltip when unaffordable.
• The amount charged equals the number printed on the Accept button. No silent overcharge.
• The price on the browse card equals the price in the negotiation modal.

Negotiation mechanics:

• Close and re-open the same listing — the same NPC returns, with the same name, traits, and prices.
• Trait badges read Impatient, not impatient.
• Counter-offers stay above the walkaway floor and the band is never degenerate.

"One shot per car" (new rule — assess how it feels, not just whether it works):

• Walk away from a negotiation → the listing is gone from the market.
• The NPC walks away on you → the listing is gone.
• Is losing a car permanently to a failed haggle tense or punishing? This is a product signal — say so either way.

UI:

• Location cards show full content (photo + name + tags + travel info) at various viewport sizes and zoom levels.
• Toasts appear bottom-centre; modals are legible at the new 0.25 overlay opacity.