Add p4, the one close anchor — the wild night is now winnable (gate 1)

SPRINT6 gate 1's anchor lever, placed by measurement rather than by guess.

The wild night had no winnable line for a geometric reason: every anchor near
the bed (p1/p2/p3) is SOUTH of it, and nothing stands north short of the house
10 m away. So covering rigs had to span the yard and died, while rigs small
enough to survive sat beside the bed rather than over it. p4 supplies the
missing north-west corner.

Its position is swept, not chosen. Against the smallest quad covering 90% of the
bed: (-2.2,-1.2) → 44.4 m², (-3.2,-1.2) → 48.6, (-3.2,-2.0) → 51.7, beyond
z=-4 → no effect at all. Pulling it inward to 44.4 would put full coverage
INSIDE the survivable band and collapse DESIGN.md's central tension — covering
the bed has to cost risk. a.test.js's >45 m² floor is what shouts if anyone
moves it in. With the 8° rake the top anchor lands at (-3.72, -1.40), and full
coverage costs 51.6 m² against 63.5 before: a real new option, 19% cheaper,
still bigger than the 23-38 m² rigs that survive unaided.

Measured through the real $80 shop: t2+p3+p4+t2b, four shackles and a spare
($75), ends hp 58 with 1 corner lost — a WIN, where before every covering rig
lost 2-3 corners and ended at 36%. Hail damage falls 51 → 34 HP versus an
uncovered rig, so decision 13 is visibly doing its job.

Selftest 244/0/0; both yard tensions still green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/world/js/tests/a.test.js

@@ -234,11 +234,11 @@ export default async function run(t) {
 
   // --- anchors -------------------------------------------------------------
 
-  t.test('yard offers 11 anchors: 3 house, 5 tree, 3 post', () => {
+  t.test('yard offers 12 anchors: 3 house, 5 tree, 4 post', () => {
     const by = (type) => world.anchors.filter((a) => a.type === type).length;
     assertEq(by('house'), 3, 'house anchors');
     assertEq(by('tree'), dressed ? 5 : 2, 'tree anchors (branch_anchor_* arrive with dress())');
-    assertEq(by('post'), 3, 'post anchors — p3 added, SPRINT3 decision 2');
+    assertEq(by('post'), 4, 'post anchors — p3 (SPRINT3 dec 2), p4 (SPRINT6 gate 1)');
     const ids = world.anchors.map((a) => a.id);
     assertEq(new Set(ids).size, ids.length, `anchor ids not unique: ${ids}`);
   });

web/world/js/world.js

@@ -270,10 +270,32 @@ export function createWorld(scene, opts = {}) {
   // 6 m bed with it costs you a sail the storm will take. Full shade is meant to
   // be the expensive answer; the small quads buy survival and pay in patchy
   // shade. That IS the design (DESIGN.md, "big flat low vs small twisted steep").
+  // SPRINT6 gate 1: p4 is the ONE close anchor the balance pass allows, and its
+  // position is measured rather than guessed.
+  //
+  // The wild night had no winnable line because every anchor near the bed —
+  // p1/p2/p3 — is SOUTH of it, and nothing stands north short of the house 10 m
+  // away. So covering rigs had to span the yard and died, while rigs small
+  // enough to survive sat beside the bed instead of over it.
+  //
+  // p4 supplies the missing north-west corner. Swept its position against the
+  // smallest quad that covers 90% of the bed:
+  //     (-2.2, -1.2) → 44.4 m²   ← breaks the tradeoff (see below)
+  //     (-3.2, -1.2) → 48.6 m²   ← here
+  //     (-3.2, -2.0) → 51.7 m²
+  //     (-4.2, -3.0) → 60.0 m²
+  //     beyond ~z=-4  → 63.5 m², i.e. too far away to matter at all
+  // Full coverage costs 63.5 m² without it. At (-3.2,-1.2) that drops to 48.6 —
+  // a real new option, 23% cheaper — while still costing you a bigger sail than
+  // the 23-38 m² rigs that survive on their own. Pulling it in to (-2.2,-1.2)
+  // would put full coverage at 44.4 m², INSIDE the survivable band, which
+  // collapses DESIGN.md's central tension: covering the bed has to cost risk.
+  // a.test.js asserts that >45 m² floor, so moving this post inward goes red.
   const postSpecs = [
     { id: 'p1', x: -4.5, z: 5.5, h: 4.0 },
     { id: 'p2', x: 4.0, z: 6.0, h: 4.0 },
     { id: 'p3', x: 0, z: 7.0, h: 4.0 },
+    { id: 'p4', x: -3.2, z: -1.2, h: 4.0 },
   ];
   const RAKE = (8 * Math.PI) / 180;
   for (const spec of postSpecs) {