kanban: add explicit delete verb for archived tasks

[LeeYuHoon]

Summary

Adds hermes kanban delete <task_ids...> as a first-class subcommand that permanently deletes already-archived tasks via the existing delete_archived_task helper.

Previously, permanent deletion was only reachable through the archive flow's rm path, and there was no direct delete verb — users (and agents shelling out to the CLI) reaching for hermes kanban delete got an argparse error. This surfaces the existing, safety-checked deletion path (archived tasks only) under the verb people actually try first.

• delete refuses live tasks: each id must already be archived, mirroring the archive rm semantics.
• Prints Deleted <id> per task; exits non-zero if any id could not be deleted.

Testing

• pytest tests/hermes_cli/test_kanban_core_functionality.py -k "delete or archive_rm" — 4 passed on current main (86fb046).
• Manual smoke test: create → archive → hermes kanban delete on a real board removes the task; show returns no such task.

🤖 Generated with Claude Code

[alt-glitch]

This was generated by AI during triage.

Related to #19964: both preserve the archived-only deletion safeguard, while this PR adds the distinct hermes kanban delete command surface.

[teknium1]

Thanks for surfacing the explicit command surface. The premise is valid on current main: hermes_cli/kanban.py:692-701 exposes permanent cleanup only through archive --rm, while hermes_cli/kanban_db.py:6173-6196 already provides the archived-only deletion primitive.

Problems

• The new task-level delete action must also be added to _DELEGATED_CHILD_DENIED_ACTIONS (hermes_cli/kanban.py:1117-1146). Otherwise it bypasses the CLI fast-fail at hermes_cli/kanban.py:981-988; the DB guard still fails closed, but this new mutation verb should preserve the established CLI boundary.
• The new test covers only success. Add direct-verb coverage that rejects a live task and leaves it present, analogous to tests/hermes_cli/test_kanban_core_functionality.py:809-821.
• Add the command and its archived-only safeguard to the lifecycle reference at website/docs/user-guide/features/kanban.md:716-721.

Suggested changes

• Include "delete" in the delegated-child denied set and add a regression test for that boundary.
• Test delete <live-id> and document hermes kanban delete <id>....

Automated hermes-sweeper review.

[teknium1]

Please also add the new task-level delete action to _DELEGATED_CHILD_DENIED_ACTIONS. archive is already denied there, and the CLI fast-fail at current hermes_cli/kanban.py:981-988 should cover this destructive alias too; the DB guard remains the durable backstop.