fix tracks to all be EW. no more NS tracks

CHANGELOG.md

@@ -10,6 +10,87 @@ The target is 20 Revenue over 5 Days.
 
 ## Unreleased
 
+### The track is 45° geometry, drawn from the printed cards
+
+The prototype designer's feedback: **there are no north–south tracks.** Straight runs are always
+east–west, the east–west line sits dead centre on the card rather than biased to the top, and a
+turnout is an east–west through track plus a curved leg meeting the north or south edge at 45°, which
+must line up with the corresponding leg on the card it abuts.
+
+Measured off `docs/tracks.png` rather than inferred. Card grid lines at y = 15/164/314/464/614/764/
+914/1064/1213 on a 2136×1397 sheet; rail centres at 89.5/236/–/–/689.5/839/989/1135.5/1288.5 — the
+card's exact vertical middle, within a pixel, on every one of the nine rows. Cards are 259×150
+(aspect ≈ 1.73). Every leg crosses the middle of its edge. Four shapes exist: turnout with the leg
+off the west end, turnout with the leg off the east end, curve west↔south, curve east↔south, plus the
+plain straight. Depot, Station, Terminal, Refinery, Freighthouse, Coal Tipple, Manufacturing and Town
+are all plain east–west straights with **no diverging leg at all**.
+
+**Slope is now part of adjacency.** Name the two diagonals after the pair of arcs that mate across a
+horizontal card edge: `ne_sw` (port pairs {n,e} and {s,w}) and `nw_se` ({n,w} and {s,e}). An `sw` card
+above an `ne` card is one unbroken rail; `sw` above `nw` is a V — both cards have the port, both legs
+meet the same point on the edge, and they still do not connect. `joins(a, p, b)` in
+`src/engine/track.ts` is the single adjacency test, and every `hasPort(nb, opposite(p))` in the
+engine, the bot and the tests now goes through it. Leaving one behind reintroduces the V.
+
+**Handedness is that diagonal.** A printed card has a back: it turns 180° but never flips. So a
+straight has ONE orientation, and a curve or turnout has two — 0° sends the 45° leg south, 180° sends
+it north, and neither changes diagonal. Left-hand reaches `sw`/`ne`, right-hand `se`/`nw`. That is
+what makes the 4-left/4-right split of the curve and turnout supply mean something: a run-around needs
+one card of each hand — a left turnout down, its matching left curve, straights along, a right curve
+back up into a right turnout. `variantsFor` takes a `hand` argument for this reason.
+
+**What went, and what opened.** `TrackAxis` and every `axis` field are deleted outright — there is
+one axis now, and a one-valued field invites the old branching back; deleting it turned `tsc` into
+the migration checklist. The Office's `e-s`/`w-s` stubs are gone, as are north–south facility
+placements. Q7's "a district hangs below the Running Track" is lifted: a turnout turned 180° reaches
+north, so `placementCandidates` and `adjacentFacilityCoord` no longer reject the rows above, and §9's
+"nine nearby spots" really is nine. `legalIntents` offered six variants per placement per card; the
+widest set is now two.
+
+**The renderer draws the card rather than approximating it.** `RAIL` moves from 30 to `H/2`, and the
+card widens from 132×96 to 166×96 to match the sheet's 1.73 — the aspect is not decoration, since the
+frog where a 45° leg meets the through track sits `H/2` from the centre and a squarer card pushes it
+almost to the edge. The fixed elbow at `(W/2, RAIL + (H-RAIL)/2)` is replaced by the real frog at
+`(W/2 ± H/2, H/2)` and a segment at exactly 45° to the edge midpoint. That elbow sat *below* the rail
+on the assumption everything diverged downward, so a leg reaching north was drawn as a hook that
+dropped past the rail and came back up. Four tests in `test/web.test.ts` now measure the emitted SVG:
+the through rail level and centred and spanning the full card, every leg at 45°, `ne`/`sw` on one
+diagonal and `nw`/`se` on the other, and the leg crossing the edge at its midpoint. The enhancement
+label moved above the rail, where it used to print along it.
+
+**Measured, 100 solitaire Standard games, against the same run before the change:**
+
+| | before | after |
+| --- | ---: | ---: |
+| mismatched 45° joints on finished boards | — | **0** |
+| district size | 25.4 cards | 28.5 |
+| mean max depth off the main | 2.38 rows | 1.45 |
+| built above the Running Track | 0/100 games | 93/100 |
+| straights laid | 1.01/game | 3.44 |
+| districts with a run-around | 99/100 | 70/100 |
+| facilities on a run-around | 0.82/game | 0.51 |
+| revenue | 7.34 mean | 5.80 |
+
+The shallower districts are intrinsic: no card joins north to south, so descending a row costs at
+least two cards — the leg out, then a curve turning the run back east–west. Districts are now wide
+and shallow, which is what the printed sheet and a real yard both look like, and the run along the
+siding is straights, which is why the bot lays three times as many (13 of the 18 enhancement cards
+need one).
+
+**The revenue and run-around drops are honest, not a regression to chase.** A run-around costs more
+pieces than it did, and the Office no longer offers a free way back up onto the main — it used to
+carry `e-s`/`w-s` stubs, so every district had one guaranteed climbing point. Two bot heuristics were
+tried against it and both rejected on measurement: preferring one side of the main changed nothing at
+−4 and made things worse at −100 (62/100 run-arounds), and paying more for the second turnout that
+closes a siding bought 86/100 run-arounds and 1.08 facilities on a loop but cost 9% of revenue
+(5.80 → 5.25). Revenue is the game's own measure, and both structural floors in `test/sim.test.ts`
+still pass, so neither shipped.
+
+The bot is otherwise rewritten around the new geometry: `descendFrom`/`waysOff`/`reachableOffMain`/
+`runAroundCells` take a side rather than assuming "below", the arc score asks `joins` instead of
+reading the arc name, and `arcsLeft` is asked per hand — a left-hand turnout's leg can only be
+continued by a left-hand curve, and a supply full of right-hand ones is no help to it.
+
 ### Q13 — a train that catches the one ahead runs into it
 
 Answered, and implemented as option B: **collide on catching up**, which is the version that rewards