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.

scripts/type-equiv.manifest.json

@@ -91,6 +91,7 @@
     { "doc": "docs/core-data-structures/bash.md", "symbol": "BashProcess", "source": "packages/bash/bash/src/types.ts" },
     { "doc": "docs/core-data-structures/bash.md", "symbol": "BashProcessRead", "source": "packages/bash/bash/src/types.ts" },
 
+    { "doc": "docs/core-data-structures/tasks.md", "symbol": "TaskKindMap", "source": "packages/tasks/tasks/src/types.ts" },
     { "doc": "docs/core-data-structures/tasks.md", "symbol": "TaskStart", "source": "packages/tasks/tasks/src/types.ts" },
     { "doc": "docs/core-data-structures/tasks.md", "symbol": "TaskHooks", "source": "packages/tasks/tasks/src/types.ts" },
     { "doc": "docs/core-data-structures/tasks.md", "symbol": "TaskOutcome", "source": "packages/tasks/tasks/src/types.ts" },