refactor(subprocess): the dispose ladder moves to its one consumer

SubprocessHandle loses dispose(graces) and SubprocessDisposeGraces: the
stdin-EOF→SIGTERM→SIGKILL sequence is teardown POLICY encoding one
consumer's cooperation shape, not process vocabulary — the seam keeps
kill/terminate/waitForExit, and waitForExit(signal?) is the quiescence
probe a consumer ladder needs. dsh-subagent-acp owns disposeAcpChild()
over those public verbs (tier tests move into its suite; a never-exits
stub pins the fail-loud path); dsh-subprocess-local sheds the ladder,
its deadline import, and the dsh-timeout dependency. Every future
backend now owes four verbs and no teardown policy. New bilingual
ladder-ownership Agent Note records the decision; catalogs regenerated.

scripts/type-equiv.manifest.json

@@ -1303,11 +1303,6 @@
       "doc": "docs/core-data-structures/subprocess.md",
       "symbol": "SubprocessCollectedOutputs",
       "source": "packages/subprocess/subprocess/src/types.ts"
-    },
-    {
-      "doc": "docs/core-data-structures/subprocess.md",
-      "symbol": "SubprocessDisposeGraces",
-      "source": "packages/subprocess/subprocess/src/types.ts"
     }
   ]
 }