workflow: rename dsh-workflow-vm to dsh-workflow-workerthread

Pure mechanical rename now that the package's internals are the
worker-thread engine: directory, package name, spec/e2e filenames,
module tags and logger prefixes, tsconfig/knip/run-gates/AGENTS.md
references, example cordis.yml plugin ids, doc links; catalogs
regenerated and the lockfile refreshed.

examples/coding-agent/cordis.yml

@@ -107,8 +107,8 @@
 # subagent backend above, plus the model-facing `workflow` tool. The model
 # writes a JavaScript orchestration script (meta + body); the engine runs it
 # in its own worker thread and fans agent() calls out as spawn children.
-- id: workflow-vm
-  name: '@deepseek-ai/dsh-workflow-vm'
+- id: workflow-workerthread
+  name: '@deepseek-ai/dsh-workflow-workerthread'
   config:
     provider: spawn