fix(tasks): address task API review feedback

The public kill result used the awkward phrase already-terminal. Rename it to already-finished and keep the model-facing response aligned; not-alive would be inaccurate because a force-failed registry record can still correspond to orphaned producer work.

Task kinds were open strings even though producer namespaces are an extension point. Add the merge-extensible TaskKindMap and derived TaskKind, cover consumer declarations in task and bundle tests, and retain the runtime non-empty check for untyped callers.

With exactOptionalPropertyTypes, owner?: Agent | undefined allowed an explicit undefined value that no caller needs. Tighten the property to owner?: Agent so unowned work is expressed by omitting it.

Record the requested task-service/backend split as a follow-up, using a systemd-backed runtime as a concrete candidate without guessing its durability and ownership contract in this PR. Regenerate the type and Cordis catalogs so public docs match the declarations.

packages/tasks/tool-tasks/tests/tool-tasks.spec.ts

@@ -192,7 +192,7 @@ describe('task_kill', () => {
     expect(p.cancels).toEqual(['superseded'])
   })
 
-  it('reports an already-terminal task without consuming its pending delta', async () => {
+  it('reports an already-finished task without consuming its pending delta', async () => {
     const { ctx } = await setup()
     let delta = 'unread tail'
     const p = producer({ readOutput: () => { const d = delta; delta = ''; return d } })