test(cliffs): pin the SHAPE of the orientation residual (#84)

[wormeyman]

cliffOrientationOracle.spec.ts counts the residual and bounds it. This pins what it looks like, because the shape is the lead and a change in shape is a change in cause even when the count holds.

Measured after #83, #86 and #90:

• 37 of 1531 matched cells, all differing in exactly ONE edge. Not one two-edge difference survives; before fix(cliffs): multisample offsets are in GRID UNITS - #18 root cause #83 the dominant mode was two edges (125 of 175), a whole corner on the wrong side of a band.
• Every one is an OVER-detection — the game reports -to-none, the port reports a crossing on that edge. Never the reverse.
• Spread over all four edges (L11/R6/T7/B13) and all three regions (7/26/4), so it is not a directional off-by-one.

Two causes are already eliminated, which is why this is worth pinning rather than re-deriving:

• crossesCliff is exact. Disassembled at 0x10160c914 under 2.1.12 (the VA in the notes had moved); cliffPlacement.ts reproduces it line for line — the a < 0 || b < 0 early-out, the boundary < e0 check, the strict > 0.5 gate and strict crossing comparisons.
• cliffiness_basic is exonerated. Substituting the game's own corner cliffiness leaves the count at exactly 37/1531.

So the residual is in the grid-4 cliff-elevation field — the one input with no direct per-corner oracle. A single-edge, strictly one-directional over-detection is what a small positive field offset looks like.

The direction assertion is the load-bearing one: if under-detections ever appear, the cause has changed and that reading is dead.

pnpm run verify green: 1315 passed / 3 skipped, 0 warnings.

🤖 Generated with Claude Code

https://claude.ai/code/session_01WRKSNgkidxc6daeHGJHqpt