refactor(subprocess): rename the process seam to subprocess and address review

Review feedback (tianyicui): 'process' is a poor service name. The family is
now packages/subprocess/ — @deepseek-ai/dsh-subprocess (ctx.subprocess,
abstract SubprocessService, Subprocess* vocabulary) and
@deepseek-ai/dsh-subprocess-local (LocalSubprocessService) — renamed
throughout code, compositions, docs (en+zh, pairs re-recorded), catalogs,
and gates. 'subprocess' is the precise term for managed OS children (the
Python-stdlib sense), avoids colliding with Node's global process object,
and reads as one system beside dsh-subagent-subprocess.

ds-review-bot findings addressed:
- kill() on a settled handle is now a no-op (no signal to a possibly-reused
  pgid, no referenced grace timer delaying exit); pinned by a spy test.
- The moved DshEnvironmentKey/DshEnvironment/CollectedOutput types get
  drift-checked type-equiv blocks on the new subprocess.md page, restoring
  their manifest registration.
- subprocess.md is registered in the core.md sub-page index (en+zh).

apps/cli/cordis.yml

@@ -89,8 +89,8 @@
   name: '@deepseek-ai/dsh-workspace'
 
 # Managed child-process groups for the bash executor (spawn/kill/output plumbing).
-- id: processes
-  name: '@deepseek-ai/dsh-process-local'
+- id: subprocess
+  name: '@deepseek-ai/dsh-subprocess-local'
 
 - id: bash-local
   name: '@deepseek-ai/dsh-bash-local'

apps/cli/package.json

@@ -42,7 +42,7 @@
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-llm-deepseek": "workspace:^",
     "@deepseek-ai/dsh-paths": "workspace:^",
-    "@deepseek-ai/dsh-process-local": "workspace:^",
+    "@deepseek-ai/dsh-subprocess-local": "workspace:^",
     "@deepseek-ai/dsh-session": "workspace:^",
     "@deepseek-ai/dsh-session-persistence-jsonl": "workspace:^",
     "@deepseek-ai/dsh-session-title": "workspace:^",