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.

.agents/notes/implemented/architecture/2026-07-26-subprocess-seam.md

@@ -12,7 +12,7 @@ English | [中文](2026-07-26-subprocess-seam.zh.md)
 
 A new `subprocess/` capability family owns "run and manage a process"; the bash family keeps "run a bash command" and consumes it:
 
-- **`@deepseek-ai/dsh-subprocess` (interface)** — the abstract `SubprocessService` owning `ctx.subprocess` with one method, `spawn(spec): SubprocessHandle`, and the shared vocabulary: the fully-explicit `SubprocessSpawnSpec` (argv, cwd, per-stream caps, spill cap, grace — no defaults; deployment-varying knobs stay with the calling seam's config, per the `dsh-bash` request/spec template and the no-hidden-defaults rule), `SubprocessHandle` with non-consuming offset-based readers, `SubprocessOutcome` with deliberately no timeout/cancel classification, and the `DSH_ENV_PREFIX`/`DshEnvironment`/`CollectedOutput` types. `argv` is never shell-interpreted.
+- **`@deepseek-ai/dsh-subprocess` (interface)** — the abstract `SubprocessService` owning `ctx.subprocess` with one method, `spawn(spec): SubprocessHandle`, and the shared vocabulary: the fully-explicit `SubprocessSpawnSpec` (argv, cwd, per-stream stdio dispositions, grace — no defaults; deployment-varying knobs stay with the calling seam's config, per the `dsh-bash` request/spec template and the no-hidden-defaults rule), `SubprocessHandle` with non-consuming offset-based readers, `SubprocessOutcome` with deliberately no timeout/cancel classification, and the shared scrub plus `DSH_ENV_PREFIX`/`DshEnvironment`/`CollectedOutput` types. `argv` is never shell-interpreted. (The [consumer-migration Agent Note](2026-07-26-subprocess-consumer-migration.md) later widened the stdio and termination vocabulary Node-ward.)
 - **`@deepseek-ai/dsh-subprocess-local` (implementation)** — `LocalSubprocessService` over the former `run.ts` plumbing (`spawn.ts`): detached groups, tail-keep truncation with private bounded spill files, credential scrub with the two-channel `DSH_*` merge, group kill escalation, and disposal that kills and joins every still-running managed process. It has no config; every limit arrives on the spec. The terminal `ENV_OVERRIDES` (`TERM=dumb` etc.) did NOT move — that is bash-tool presentation policy and stays in `dsh-bash-local`, merged through the ordinary env channel.
 - **`dsh-bash-local` (consumer)** — `inject: ['subprocess']`; maps each resolved `BashExecSpec` onto a `SubprocessSpawnSpec` (`['bash', '-c', command]`), keeps its config, `resolve()` defaulting, fused-deadline `timedOut`/`aborted` classification, the `[stderr]`-marked background read merge with its consuming cursor, and the `onProcessDone` subclass hook. `dsh-bash-sandbox` is unchanged apart from redeclaring the inherited inject; it still wraps at the command-string level and re-enters the inherited spawn path.
 - **`dsh-bash` (seam)** — re-exports the moved vocabulary from `dsh-subprocess`, so no bash consumer changes an import; `BashExecRequest`/`BashExecSpec`/`BashProcess` and the sandbox facts remain bash-owned.
@@ -25,7 +25,7 @@ Background-process lifetime moved from the executor to the subprocess service: t
 
 **Leave the process plumbing inside `dsh-bash-local` (status quo).** Rejected for the same reason the [task registry split](2026-07-26-task-registry-seam.md) landed: the boundary is stable and already documented in-code (`run.ts`'s module doc said "this layer reacts to an abort signal; the executor owns deadlines and classifies causes"), and keeping it private makes every future non-shell runner either fork the mechanics or depend on a bash-named package for non-bash work. The user-visible driver for this stack was exactly this split.
 
-**Migrate the repo's other spawn sites (lsp-local, pty-local, subagent-subprocess, sdk package-manager, test-support launchers) onto `ctx.subprocess` in the same change.** Rejected as scope creep with real design risk: those sites have materially different stream and lifecycle needs — node-pty ownership (pty), LSP framing over long-lived stdio with tree-kill fallbacks (lsp), stdin-EOF-first disposal ladders and no output buffering (subagent transports) — and forcing them under a handle shaped for bounded batch output would either bloat the seam or misfit the consumers. The seam ships proven against its one real consumer family, per the shape-interfaces-around-current-consumers rule; the others are named as deferred work in the seam README.
+**Migrate the repo's other spawn sites (lsp-local, pty-local, subagent-subprocess, sdk package-manager, test-support launchers) onto `ctx.subprocess` in the same change.** Rejected as scope creep with real design risk at this PR's scale: those sites have materially different stream and lifecycle needs — node-pty ownership (pty), LSP framing over long-lived stdio with tree-kill fallbacks (lsp), stdin-EOF-first disposal ladders and no output buffering (subagent transports) — and forcing them under a handle shaped for bounded batch output would either bloat the seam or misfit the consumers. The seam shipped proven against its one real consumer family, per the shape-interfaces-around-current-consumers rule. Review then asked for exactly that follow-up as a stacked PR; the [consumer-migration Agent Note](2026-07-26-subprocess-consumer-migration.md) records the Node-ward reshape and which sites moved (and which stayed, by ownership).
 
 **Put `run_in_background`/task semantics into the process seam instead.** Rejected: that boundary already exists — `ctx.tasks` owns ids, ownership, and notices, and the bash tool adapts a `BashProcess` into task hooks. The process seam sits *below* the bash executor, not beside the task registry.