refactor: rename the backend to dsh-subagent-dsh-sdk

The group's convention is package suffix == provider default
(subagent-acp/'acp', subagent-spawn/'spawn', subagent-fork/'fork'), and the
provider default became dsh-sdk in the last review round — so the package
follows: @deepseek-ai/dsh-subagent-dsh-sdk at
packages/subagent/subagent-dsh-sdk, plugin name subagent-dsh-sdk,
diagnostics prefixed subagent-dsh-sdk:. The dsh echo has precedent
(dsh-llm-deepseek). Directory, fixture path, knip/tsconfig/examples
registrations, catalogs, READMEs (en+zh), and the Agent Note follow; the
sdk-client dispose ladder moves to its own module (src/dispose.ts) with the
deterministic FakeChild tier tests restored alongside it.

packages/sdk/sdk-client/src/client.ts

@@ -21,6 +21,7 @@ import {
   type SessionPromptParams,
 } from '@deepseek-ai/dsh-sdk-protocol'
 import type { ContentBlock } from '@deepseek-ai/dsh-llm'
+import { disposeRuntimeProcess } from './dispose.ts'
 import type { HarnessClientOptions, HarnessNotification, NotificationFilter } from './types.ts'
 
 /** Retained stderr lines used to diagnose an unexpected runtime death. */
@@ -447,91 +448,6 @@ export function isRecord(value: unknown): value is Record<string, unknown> {
   return typeof value === 'object' && value !== null && !Array.isArray(value)
 }
 
-/**
- * Race the child's exit against a timer. Neither outcome leaves anything
- * behind on the child: the exit listener is removed on timeout and the timer
- * is cleared on exit, so the ladder's tiers never accumulate listeners.
- */
-function exitsWithin(child: ChildProcess, ms: number): Promise<boolean> {
-  if (child.exitCode !== null || child.signalCode !== null) return Promise.resolve(true)
-  return new Promise<boolean>((resolve) => {
-    const onExit = (): void => {
-      clearTimeout(timer)
-      resolve(true)
-    }
-    // `.unref()` so a pending grace timer never keeps the parent's loop alive.
-    const timer = setTimeout(() => {
-      child.removeListener('exit', onExit)
-      resolve(false)
-    }, ms).unref()
-    child.once('exit', onExit)
-  })
-}
-
-/** Force-terminate the runtime and reject if no exit edge arrives within the grace. */
-function forceTerminateWithin(child: ChildProcess, ms: number): Promise<void> {
-  if (child.exitCode !== null || child.signalCode !== null) return Promise.resolve()
-  return new Promise<void>((resolve, reject) => {
-    let accepted = false
-    let settled = false
-    const cleanup = (): void => {
-      clearTimeout(timer)
-      child.off('exit', onExit)
-      child.off('error', onError)
-    }
-    const settle = (complete: () => void): void => {
-      if (settled) return
-      settled = true
-      cleanup()
-      complete()
-    }
-    const onExit = (): void => { settle(resolve) }
-    const onError = (error: Error): void => { settle(() => { reject(error) }) }
-    child.once('exit', onExit)
-    child.once('error', onError)
-    const timer = setTimeout(() => {
-      const disposition = accepted ? 'accepted' : 'refused'
-      settle(() => {
-        reject(new Error(`runtime process did not exit within ${ms}ms after SIGKILL was ${disposition}`))
-      })
-    }, ms).unref()
-    try {
-      accepted = child.kill('SIGKILL')
-      if (child.exitCode !== null || child.signalCode !== null) settle(resolve)
-    } catch (error: unknown) {
-      settle(() => { reject(new Error('SIGKILL failed', { cause: error })) })
-    }
-  })
-}
-
-/**
- * Tear the runtime down to quiescence, resolving only after exit: close stdin
- * and allow cooperative flush, then use the host's graceful and forced
- * termination semantics. POSIX sends `SIGTERM` before `SIGKILL`; Windows
- * skips directly to forced termination because Node maps both signals to
- * `TerminateProcess`.
- * @throws When forced termination errors or the child does not report exit
- * within `disposeGraceMs`.
- */
-async function disposeRuntimeProcess(
-  child: ChildProcess,
-  graces: { disposeEofGraceMs: number; disposeGraceMs: number },
-  platform: NodeJS.Platform = process.platform,
-): Promise<void> {
-  // Already gone: nothing to reap.
-  if (child.exitCode !== null || child.signalCode !== null) return
-  // 1. Close stdin and allow cooperative teardown and durable-state flush.
-  child.stdin?.end()
-  if (await exitsWithin(child, graces.disposeEofGraceMs)) return
-  // 2. POSIX gets a catchable graceful signal; Windows signals all force-terminate.
-  if (platform !== 'win32') {
-    child.kill('SIGTERM')
-    if (await exitsWithin(child, graces.disposeGraceMs)) return
-  }
-  // 3. Force-kill and await a bounded exit edge.
-  await forceTerminateWithin(child, graces.disposeGraceMs)
-}
-
 /** The message of a thrown value (the transport only throws `Error`s; `String` covers the rest). */
 function errorMessage(error: unknown): string {
   /* v8 ignore next -- the transport and dispose ladder reject only with Errors */