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.

packages/subprocess/subprocess-local/src/spawn.ts

@@ -1,10 +1,9 @@
 /**
  * Process plumbing for the local subprocess service: detached process-tree
  * spawn with per-stream stdio dispositions, tail-keep collection with spill
- * files, tree-scoped signalling (POSIX groups; Windows taskkill), the
- * SIGTERM→SIGKILL escalation, and the cooperative EOF-first dispose ladder.
- * This layer reacts to an abort signal; callers own deadlines and classify
- * causes.
+ * files, tree-scoped signalling (POSIX groups; Windows taskkill), and the
+ * SIGTERM→SIGKILL escalation. This layer reacts to an abort signal; callers
+ * own deadlines, teardown ladders, and cause classification.
  * @module dsh-subprocess-local/spawn
  */
 
@@ -15,13 +14,11 @@ import { closeSync, mkdtempSync, openSync, unlinkSync, writeSync } from 'node:fs
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { setTimeout as sleepMs } from 'node:timers/promises'
-import { deadline } from '@deepseek-ai/dsh-timeout'
 import { DSH_ENV_PREFIX, scrubbedParentEnv } from '@deepseek-ai/dsh-subprocess'
 import type {
   CollectedOutput,
   DshEnvironment,
   SubprocessCollect,
-  SubprocessDisposeGraces,
   SubprocessHandle,
   SubprocessOutcome,
   SubprocessOutputMode,
@@ -63,9 +60,6 @@ export interface SpawnInternals {
   platform?: NodeJS.Platform
 }
 
-/** Timeout code marking a dispose-ladder tier bound (vs an external abort). */
-const DISPOSE_TIER_TIMEOUT = 'SUBPROCESS_DISPOSE_TIER'
-
 /**
  * Liveness-poll cadence for tree-exit waits. The timer stays ref'd: an
  * awaited teardown must keep the event loop alive until the tree really
@@ -469,39 +463,6 @@ export function spawnSubprocess(spec: SubprocessSpawnSpec, internals: SpawnInter
     return true
   }
 
-  /**
-   * Wait, bounded, for whole-tree exit — the dispose ladder's quiescence test.
-   * Tree liveness, not direct-child settlement: a TERM-trapping helper that
-   * outlives the leader must hold the ladder on its tier until it exits.
-   */
-  const treeExitsWithin = async (ms: number): Promise<boolean> => {
-    using bound = deadline(undefined, ms, DISPOSE_TIER_TIMEOUT)
-    return await waitForExit(bound.signal)
-  }
-
-  let disposal: Promise<void> | undefined
-  const dispose = (graces: SubprocessDisposeGraces): Promise<void> => (disposal ??= (async () => {
-    // A spawn failure has no process to tear down; observe the rejection so
-    // disposal in a finally block cannot surface it as unhandled.
-    if (pid <= 0) {
-      await done.catch(() => {})
-      return
-    }
-    // 1. Close a piped stdin and allow cooperative teardown and flush.
-    if (stdinMode === 'pipe') child.stdin?.end()
-    if (await treeExitsWithin(graces.eofGraceMs)) return
-    // 2. POSIX gets a catchable graceful signal; Windows taskkill force-terminates.
-    if (platform !== 'win32') {
-      kill('SIGTERM')
-      if (await treeExitsWithin(graces.graceMs)) return
-    }
-    // 3. Force-kill the tree and await a bounded exit edge.
-    kill('SIGKILL')
-    if (!(await treeExitsWithin(graces.graceMs))) {
-      throw new Error(`child process tree did not exit within ${graces.graceMs}ms after forced termination`)
-    }
-  })())
-
   return {
     pid,
     /* v8 ignore start -- pipe-mode fds exist on every spawn Node returns; the null-coalesces guard a nonconforming ChildProcess only. */
@@ -517,6 +478,5 @@ export function spawnSubprocess(spec: SubprocessSpawnSpec, internals: SpawnInter
     kill,
     terminate,
     waitForExit,
-    dispose,
   }
 }