feat(subprocess): migrate lsp-local, subagent-acp, and the env scrubs onto the seam

Review direction (tianyicui, PR #660): in a stacked PR, change all other
process-running places to use the new service.

- lsp-local: LspConnection spawns through ctx.subprocess (piped protocol
  streams + a no-spill collected stderr tail); its private process-tree
  helpers (POSIX group signalling, Windows taskkill, liveness polling) are
  deleted in favor of the seam's handle verbs, and its buildChildEnv now
  rides scrubbedParentEnv (LSP children also stop inheriting stale DSH_*).
  The plugin injects 'subprocess'; compositions/tests mount
  dsh-subprocess-local.
- subagent-acp: the ACP child spawns through the seam (piped ndjson streams,
  inherited stderr); spawn failure surfaces through done-rejection into the
  same startup race; disposal is handle.dispose with the plugin's configured
  graces. dsh-subagent-subprocess is DELETED — its dispose ladder and scrub
  are the seam's, and the isolated-config-dir helper had no consumer.
- mcp-client, pty-local, sdk-helper: adopt scrubbedParentEnv as the one
  scrub definition (their spawns stay put by ownership: the MCP SDK and
  node-pty own those calls; the SDK wizard runs outside any composition).
- Coverage: per-file 100% over every touched src file, with each v8 ignore
  carrying a platform or contract reason; new suites cover stdio
  dispositions, the dispose ladder tiers, injected-win32 tree semantics,
  waitForExit, settled-kill/terminate no-ops, and spawn-failure disposal.
- Docs: consumer-migration Agent Note (en; zh follows in this PR), seam note
  updated in place, subprocess.md rewritten for the reshaped vocabulary
  (type-equiv re-registered), READMEs and SERVICE_ROLES updated, taskkill
  added to knip ignoreBinaries.

scripts/gen-doc-graphs.ts

@@ -271,8 +271,8 @@ const SERVICE_ROLES: ServiceRole[] = [
     title: 'Subprocess seam',
     mode: 'seam',
     implementations: ['subprocess-local'],
-    consumers: ['bash-local', 'bash-sandbox'],
-    note: 'The bash executors spawn their process groups through ctx.subprocess; the service owns group lifetime, bounded spill-backed output, and kill escalation.',
+    consumers: ['bash-local', 'bash-sandbox', 'lsp-local', 'subagent-acp'],
+    note: 'The bash executors, the LSP host, and the ACP subagent backend spawn their children through ctx.subprocess; the service owns tree lifetime, stdio dispositions (pipes, inherit, bounded spill-backed collection), and kill escalation.',
   },
   {
     key: 'bash',

scripts/type-equiv.manifest.json

@@ -2201,6 +2201,36 @@
       "doc": "docs/core-data-structures/subprocess.md",
       "symbol": "CollectedOutput",
       "source": "packages/subprocess/subprocess/src/types.ts"
+    },
+    {
+      "doc": "docs/core-data-structures/subprocess.md",
+      "symbol": "SubprocessStdinMode",
+      "source": "packages/subprocess/subprocess/src/types.ts"
+    },
+    {
+      "doc": "docs/core-data-structures/subprocess.md",
+      "symbol": "SubprocessCollect",
+      "source": "packages/subprocess/subprocess/src/types.ts"
+    },
+    {
+      "doc": "docs/core-data-structures/subprocess.md",
+      "symbol": "SubprocessOutputMode",
+      "source": "packages/subprocess/subprocess/src/types.ts"
+    },
+    {
+      "doc": "docs/core-data-structures/subprocess.md",
+      "symbol": "SubprocessStdio",
+      "source": "packages/subprocess/subprocess/src/types.ts"
+    },
+    {
+      "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"
     }
   ]
 }

scripts/verify-package-readme-model-experience.ts

@@ -87,7 +87,6 @@ const SENTENCE_MODEL_EXPERIENCE: Readonly<Record<string, SentenceContract>> = {
   'packages/spill/spill': { kind: 'indirect', reason: 'The storage seam delegates model rendering to spill consumers.' },
   'packages/spill/spill-local': { kind: 'indirect', reason: 'The storage backend delegates model rendering to spill consumers.' },
   'packages/subagent/subagent': { kind: 'indirect', reason: 'The provider registry delegates parent-model rendering to dsh-tool-subagent.' },
-  'packages/subagent/subagent-subprocess': { kind: 'indirect', reason: 'Only process-based subagent backends compose a child model request.' },
   'packages/support/acp-snapshot': { kind: 'none', reason: 'The test harness observes and normalizes transcripts without changing live requests.' },
   'packages/support/agent-loop-testkit': { kind: 'none', reason: 'The test helper mounts services but neither drives nor modifies model requests.' },
   'packages/support/invariants': { kind: 'none', reason: 'The observer validates requests but never rewrites their context.' },