docs(subagent): correct cold-resume parent contract

The descriptor module claimed that no parent exists during cold resume, using that as the reason maxTokens cannot be inherited. Continuable follow-up actually requires and authorizes the exact live direct parent before it loads the descriptor and materializes the child, so the stated lifecycle fact was false.

Keep the real persistence decision explicit: per-activation budgets are not durable descriptor composition. Cold resume reconstructs child options only from the curated durable fields, so it deliberately neither restores the establishing budget nor inherits the live parent current transient budget; the resumed provider and model route defaults apply.

This is a contract-only correction with no runtime change. The exported JSDoc gate remains clean.

packages/subagent/subagent/src/descriptor.ts

@@ -13,9 +13,10 @@
  * `delegationDepth` as the monotone floor — and `outputSchema`, which belongs
  * to one activation's result contract rather than durable child composition.
  * Per-activation knobs such as `maxTokens` are omitted for the same reason as
- * `outputSchema`: they budget one activation and, on cold resume, no parent
- * exists to inherit them from, so the resumed activation runs under the
- * deployment defaults rather than restoring a stale budget.
+ * `outputSchema`: they budget one activation. Cold resume requires the exact
+ * live parent for authorization but reconstructs child options only from the
+ * durable descriptor, so it neither restores the prior budget nor inherits
+ * the parent's current one; the resumed route's defaults apply instead.
  *
  * @module @deepseek-ai/dsh-subagent/descriptor
  */