docs: the contract manifest stands alone; public docs describe this engine only

The manifest's prose pointer named a document that answers a confidential
specification, and such a document does not belong in a public repository even
in summary. The pointer is dropped — the manifest is generated from this
engine's own surface and is self-describing — and the requirement marking it
deliberately omits is recorded with the contract's owner rather than here.

The standard is written down so this is not relitigated per document.

scripts/emit-contract-manifest.mjs

@@ -10,8 +10,8 @@
  * between two engines, never between two authors.
  *
  * Requirement marking (required / optional per door) is NOT derivable from the
- * surface; it is a commitment, and it lives in docs/contract-1-ratification.md.
- * This manifest carries the surface; that document carries the promise.
+ * surface — it is a commitment, recorded with the contract's owner rather than
+ * here. This manifest carries the surface; the promise lives with the contract.
  *
  * Usage: node scripts/emit-contract-manifest.mjs [--check]
  *   --check exits non-zero when the committed manifest is stale.
@@ -68,7 +68,6 @@ const servedOnIndex = accepted.filter((op) => !refusedByIndex.includes(op))
 const manifest = {
   contractVersion: versionModule.contractVersion(),
   engine: '@soulcraftlabs/brainy',
-  prose: 'docs/contract-1-ratification.md',
   compatibility: {
     minor:
       'additive — a new optional door, a new served operator, a new error class; every existing implementation still conforms',