fix(invariants): assert runtime relationships, not API shapes

packages/util/retention/src/invariant.ts

@@ -1,33 +1,24 @@
-/** Package-owned runtime contracts for @deepseek-ai/dsh-retention. @module @deepseek-ai/dsh-retention/invariant */
+/**
+ * Package-owned invariant companion for `@deepseek-ai/dsh-retention`.
+ * @module @deepseek-ai/dsh-retention/invariant
+ */
 
 /* jscpd:ignore-start */
 import type { Context } from 'cordis'
-import { assertInvariant, type InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+import type { InvariantInstaller } from '@deepseek-ai/dsh-invariants'
 
 const PACKAGE_NAME = '@deepseek-ai/dsh-retention'
 
 /** Cordis companion plugin name. */
 export const name = 'retention-invariant'
-/** Services required before the companion can register. */
+/** Service required before the companion can reserve package ownership. */
 export const inject = ['invariants']
 
-/** Assert exact head-retention accounting after the budget is exceeded. */
-const install: InvariantInstaller = async (_ctx, fail) => {
-  const { ItemRetainer } = await import('./index.ts')
-  const retainer = new ItemRetainer<string>({ kind: 'head', maxItems: 2 })
-  retainer.push('first')
-  retainer.push('second')
-  retainer.push('third')
-  const result = retainer.finish()
-  assertInvariant(fail,
-    result.items.join(',') === 'first,second'
-      && result.seen === 3
-      && result.kept === 2
-      && result.truncated
-      && result.omitted.kind === 'exact'
-      && result.omitted.count === 1,
-    'head retention must keep the prefix and report exact seen, kept, and omitted counts')
-}
+/**
+ * No runtime invariant: this pure utility owns no event stream or mutable runtime data; its value
+ * algebra is enforced by unit tests.
+ */
+const install: InvariantInstaller = () => {}
 
 /**
  * Register this package's invariant companion.