fix: close both code-review mediums and drop the dead paper layer (#302 r1 M1,M2)

**M1.** `docs/WALL-THICKNESS.md` §3 «Junction nodes» переписан под решение №5:
полный mitre, фаска #249 в отставке, `bevelMultiWallBody` — только адресный
латеральный трим. Прежний абзац описывал отменённое утреннее решение.

**M2.** Guard мутанта `junction-fans-disabled` собирает `test-build` и бандл
перед смоком: `smoke_junction_holes` — единственный смок, импортирующий из
`test-build`, и в чистом worktree он падал `ERR_MODULE_NOT_FOUND` до
применения мутации. Ревью прав: после переякорения guard'а на смок я не
перегнал его штатным харнесом — только ручной test-build-патч, который worktree
не видит.

**Low + следствие.** `bevelMultiWallPaper` удалена как мёртвый код; следом
измерено (фикстура #197 и репро владельца — байт в байт с веерами и без), что
и `paperWithNodeCorners` бумаге ничего не даёт: footprint ∪ shell уже
покрывает каждый узел. Слой удалён целиком, бумага возвращена к rawPaper.
Осиротевший мутант `multi-wall-paper-full-origin-cut` (#261, «белый клин от
вычитающего разреза бумаги») снят с обоснованием: в бумаге не осталось ни
одного вычитания — этот класс регресса невозможен по построению.

`npm test` 1303/1303; `golden:verify` 126/126; контракт-проба репро — 0.

Issue: #302
User-Visible: no

docs/WALL-THICKNESS.md

@@ -185,18 +185,21 @@ excluded from this shared `roomGeom`, so a door does not change the room fill
 and a detached body cannot punch it. Full and Static render paths reuse the same
 structural cache instead of rebuilding wall booleans once per room.
 
-**Junction nodes (#302).** A degree-3+ node keeps the approved #249 chamfer
-(`bevelMultiWallBody`, bounded by the node's join limit
-`MULTI_WALL_JOIN_LIMIT × halfDepth`), and AFTER it the node additively gets
-back what a chamfer must never eat: the exact support quads of its rays (each
-bounded by its own finite length, so a trimmed lateral phantom — #271 — cannot
-come back) and one sector fan per pair of angularly adjacent rays
-(`junctionNodeGeometry`): mitre up to the node limit, bevel chord past it,
-reflex sectors skipped. The pieces are clipped by the plain-corner facade
-bound (`junctionNodeBound`), so a node can never grow new facade at a concave
-vertex. The result is strip-safe: an acute junction is solid masonry, and the
-objective invariant «body ⊇ support strips ∪ fans, inside the facade bound» is
-machine-checked by `junctionContractHoles` in tests and the
+**Junction nodes (#302, owner decision #5).** A degree-3+ node closes with a
+FULL mitre, like an ordinary wall intersection on a drawing — the #249 chamfer
+is retired. For every pair of angularly adjacent rays `junctionNodeGeometry`
+builds one additive fan: the mitre is accepted when it sits IN the sector
+(forward along the rays for an ordinary pair, backward for a reflex outer
+corner), within the classic `MITRE_LIMIT` and never past a ray's thick
+support (#271); a reflex pair without a valid mitre closes with the plain
+chord, an ordinary one with a local bevel bounded by the support, the limit
+and twice the pair's depth. The node also gets the exact support quads of its
+rays. All pieces are clipped by the plain-corner facade bound
+(`junctionNodeBound`), so a node cannot grow new facade at a concave vertex.
+`bevelMultiWallBody` survives only as a TARGETED lateral trim for nodes with a
+degenerately short thick support (#271); every other node is purely additive.
+The objective invariant «body ⊇ support strips ∪ fans, inside the facade
+bound» is machine-checked by `junctionContractHoles` in tests and the
 `smoke_junction_holes` wiring probe. Degenerate zero-area rings left by
 coincident chords are dropped.
 

scripts/mutation-gate.mjs

@@ -614,45 +614,6 @@ export const MUTANTS = [
       replace: '  return v;',
     }],
   },
-  {
-    id: 'multi-wall-paper-full-origin-cut',
-    guard: 'npx tsc -p tsconfig.test.json && node scripts/fix-test-build.mjs '
-      + '&& node --test --test-name-pattern="issue #197 keeps" '
-      + 'test/wall-thickness.test.mjs',
-    because: 'the exterior paper must retain valid multi-wall overlap up to R; cutting from the '
-      + 'offset origins recreates the measured white T-junction wedge from #261',
-    patches: [{
-      file: 'src/wall-thickness.ts',
-      find: '      const cuts = multiWallEffectiveCutGeometry(\n'
-        + '        node, map, true, true, protectedStrips,\n'
-        + '      );',
-      replace: '      const cuts = multiWallEffectiveCutGeometry(\n'
-        + '        node, map, false, true, protectedStrips,\n'
-        + '      );',
-    }, {
-      file: 'src/wall-thickness.ts',
-      find: '      if (envelope) localInside = intersection(localInside, envelope);\n'
-        + '      else if (centre) localInside = intersection(localInside, centre);',
-      replace: '      if (centre) localInside = intersection(localInside, centre);\n'
-        + '      else if (envelope) localInside = intersection(localInside, envelope);',
-    }, {
-      file: 'src/wall-thickness.ts',
-      find: '  return cuts && protectedStrips ? difference(cuts, protectedStrips) : cuts;',
-      replace: '  return cuts;',
-    }, {
-      file: 'src/wall-thickness.ts',
-      find: '      if (protectedStrips) local = union(local, protectedStrips);',
-      replace: '      // protected-strip fail-safe intentionally disabled by the mutant',
-    }, {
-      file: 'src/wall-thickness.ts',
-      find: '  if (protectedStrips) {\n'
-        + '    try {\n'
-        + '      let protectedInside = protectedStrips;',
-      replace: '  if (protectedStrips && false) {\n'
-        + '    try {\n'
-        + '      let protectedInside = protectedStrips;',
-    }],
-  },
   {
     id: 'multi-wall-orthogonal-strip-protection-disabled',
     guard: 'npx tsc -p tsconfig.test.json && node scripts/fix-test-build.mjs '
@@ -2211,7 +2172,9 @@ export const MUTANTS = [
   },
   {
     id: 'junction-fans-disabled',
-    guard: 'node demo/smoke_junction_holes.mjs',
+    guard: 'npx tsc -p tsconfig.test.json && node scripts/fix-test-build.mjs '
+      + '&& npm run build >/dev/null 2>&1 && cp dist/houseplan-card.js demo/srv/assets/houseplan-card.js '
+      + '&& node demo/smoke_junction_holes.mjs',
     because: 'без вееров сектор между соседними полосами узла остаётся дырой — '
       + 'это и есть класс артефактов #302',
     patches: [{

src/wall-thickness.ts

@@ -2952,40 +2952,6 @@ function bevelMultiWallBody(
   return current;
 }
 
-function bevelMultiWallPaper(
-  paper: any,
-  centre: any,
-  map: MultiWallNodeMap,
-): any {
-  let beveled = paper;
-  let protectedStrips: any = null;
-  try {
-    protectedStrips = multiWallProtectedMapGeometry(map);
-  } catch {
-    return paper;
-  }
-  for (const node of map.nodes) {
-    try {
-      const cuts = multiWallEffectiveCutGeometry(
-        node, map, true, true, protectedStrips,
-      );
-      if (cuts) beveled = difference(beveled, cuts);
-    } catch {
-      // Isolate a failed optional node cut; retain the last valid paper.
-    }
-  }
-  try {
-    if (protectedStrips) {
-      const protectedPaper = intersection(protectedStrips, paper);
-      beveled = union(beveled, protectedPaper);
-    }
-    // Paper is the complete room footprint. Interior bevel cuts expose floor,
-    // not the scene background, so the centre union must always remain solid.
-    return union(centre, beveled);
-  } catch {
-    return paper;
-  }
-}
 
 /**
  * Collapse arithmetic noise on computed junction vertices before polyclip sees
@@ -3191,15 +3157,7 @@ export function floorFootprintGeometry(
     const paper = exterior.shell?.length
       ? union(exterior.centre, exterior.shell)
       : exterior.centre;
-    return multiWallNodes.nodes.length
-      ? paperWithNodeCorners(
-        paper, multiWallNodes,
-        junctionNodeBound(
-          rooms, walls, openCuts, pitch, cellCm, gridPitch, coordScale,
-          multiWallNodes,
-        ),
-      )
-      : paper;
+    return paper;
   } catch {
     return null;
   }
@@ -3260,19 +3218,6 @@ export function junctionNodeBound(
   }
 }
 
-/** Paper under the node corner: the same additive supports and fans (#302). */
-function paperWithNodeCorners(paper: any, map: MultiWallNodeMap, bound?: any): any {
-  const corners = junctionNodeGeometry(map);
-  let out = paper;
-  for (const piece of [...corners.supports, ...corners.fans]) {
-    try {
-      let ring: any = [closedRing(piece)];
-      if (bound) ring = intersection(ring, bound);
-      if (ring?.length) out = union(out, ring);
-    } catch { /* keep paper */ }
-  }
-  return dropDegenerateRings(out, Math.max(map.epsilon, 1e-9) ** 2);
-}
 
 export function polyclipToPathD(geom: any): string {
   if (!geom) return '';
@@ -3520,15 +3465,11 @@ export function wallBodiesGeometry(
       : [];
     // Paper: the approved chamfer first, then the same additive fans that
     // complete the masonry corner complete the paper beneath it (#302).
-    const paperGeom = multiWallNodes.nodes.length
-      ? paperWithNodeCorners(
-        rawPaperGeom, multiWallNodes,
-        junctionNodeBound(
-          rooms, walls, openCuts, pitch, cellCm, gridPitch, coordScale,
-          multiWallNodes,
-        ),
-      )
-      : rawPaperGeom;
+    // Paper needs no node pieces: the footprint-plus-shell union already
+    // covers every junction (measured on #197 and the owner repro — byte-equal
+    // with and without them), and with the subtractive paper bevel gone the
+    // #261 white-wedge class is impossible by construction.
+    const paperGeom = rawPaperGeom;
     const bodyOf = (ring: typeof roomRings[number]): any => {
       const outset: any = closedRing(ring.outset);
       return ring.inset ? difference(outset, closedRing(ring.inset) as any) : outset;
@@ -3972,15 +3913,7 @@ export function paperRoomShapesWithWalls(
       const multiWallNodes = multiWallNodesForGeometry(
         rooms, walls, openCuts, pitch, cellCm, gridPitch, coordScale,
       );
-      const paper = multiWallNodes.nodes.length
-        ? paperWithNodeCorners(
-          rawPaper, multiWallNodes,
-          junctionNodeBound(
-            rooms, walls, openCuts, pitch, cellCm, gridPitch, coordScale,
-            multiWallNodes,
-          ),
-        )
-        : rawPaper;
+      const paper = rawPaper;
       const path = polyclipToPathD(paper);
       if (path) return [{ path }];
     }