test(tools): make the deep oneOf-object test a real quadratic tripwire

The 60k oneOf-object test had only one object node (the innermost), so the
pre-fix code called allocateClassName once — linear, never tripping the
timeout, so it did not cover the class-name Θ(depth²) it named. Give every
level an object branch (both oneOf arms are objects) so each level propagates
a one-segment-longer class name; the pre-fix rope slice is then Θ(depth²)
(~9.5s, past the 5s default) while the capped path stays linear. Also extract
the shared cap expression into capClassNameBase (used by allocateClassName and
childClassName). py-types.ts stays at 100% per-file coverage.

packages/core/tools/src/py-types.ts

@@ -125,6 +125,11 @@ function camelCase(raw: string): string {
 /** Class-name base cap keeping each emitted name — and total text — linear in schema depth. */
 const MAX_CLASS_NAME_BASE = 120
 
+/** Cap a class-name base at {@link MAX_CLASS_NAME_BASE} (see the callers for why capping keeps the render linear). */
+function capClassNameBase(base: string): string {
+  return base.length > MAX_CLASS_NAME_BASE ? base.slice(0, MAX_CLASS_NAME_BASE) : base
+}
+
 /**
  * Reserve a unique class name from a base, suffixing `2`, `3`, … on collision.
  * The base is capped at {@link MAX_CLASS_NAME_BASE} first: child class names
@@ -137,7 +142,7 @@ const MAX_CLASS_NAME_BASE = 120
  * (amortized) instead of Θ(depth²) in time.
  */
 function allocateClassName(base: string, state: RenderState): string {
-  const capped = base.length > MAX_CLASS_NAME_BASE ? base.slice(0, MAX_CLASS_NAME_BASE) : base
+  const capped = capClassNameBase(base)
   let name = capped
   if (state.usedClassNames.has(name)) {
     let n = state.nextClassCounter.get(capped) ?? 2
@@ -158,8 +163,7 @@ function allocateClassName(base: string, state: RenderState): string {
  * The bounded base plus the collision counter still yields unique names.
  */
 function childClassName(base: string, segment: string): string {
-  const joined = `${base}${segment}`
-  return joined.length > MAX_CLASS_NAME_BASE ? joined.slice(0, MAX_CLASS_NAME_BASE) : joined
+  return capClassNameBase(`${base}${segment}`)
 }
 
 /**