fix(desktop): archive kanban boards from Board settings

[Per0-1]

Summary

Desktop Kanban Board settings only allowed renaming and project binding. There was no way to remove a board from the Desktop UI, even though:

• browser dashboard already has Archive for non-default boards
• backend already exposes DELETE /api/plugins/kanban/boards/{slug} (archive by default)
• CLI already has hermes kanban boards rm <slug>

This adds Desktop parity: Archive board in Board settings (destructive, confirmed), hidden on default. Hard-delete remains CLI-only (--delete / ?delete=true).

Changes

• apps/desktop/src/plugins/kanban/api.ts — archiveBoard(slug) → DELETE /boards/{slug}
• apps/desktop/src/plugins/kanban/board-switcher.tsx — Archive button + ConfirmDialog; switch away if the active board was archived
• apps/desktop/src/plugins/kanban/i18n.ts — en/ja/zh/zh-hant strings

Test plan

• Open Kanban → board switcher → Board settings… on a non-default board
• Confirm Archive board appears (left, destructive) and is absent on default
• Cancel the confirm dialog → board unchanged
• Confirm archive → board leaves the switcher list; if it was active, UI falls back to the server current board (usually default)
• Board dir lands under ~/.hermes/kanban/boards/_archived/
• hermes kanban boards list no longer shows the archived slug

[spfcraze]

This was generated by AI during triage.

Summary:
The Archive button this adds calls the same DELETE /boards/{slug} endpoint whose archived boards the gateway dispatcher is documented to silently recreate while the gateway runs (#67888, #35211, #43243) — so the test plan's "board leaves the switcher list" step can fail under the default configuration.

Problems:

• gateway/kanban_watchers.py enumerates list_boards(include_archived=False) and calls _kb.connect(board=slug) per board each tick (lines 1303, 1240); connect() recreates a missing board directory via path.parent.mkdir(parents=True, exist_ok=True) (hermes_cli/kanban_db.py:2176) — the concurrent-connect window remove_board's own comment names at hermes_cli/kanban_db.py:878.
• The desktop plugin reuses the dashboard's /api/plugins/kanban/* router as-is (apps/desktop/src/plugins/kanban/api.ts), so the button rides the same backend path the dashboard Archive control uses — the surface [Bug]: Kanban boards cannot be removed from the dashboard because archived boards are recreated #81021 reports as reappearing after archive.
• kanban.dispatch_in_gateway defaults to true (hermes_cli/config_defaults.py), so the dispatcher watcher runs in the gateway the desktop plugin talks to; the open fix fix: prevent archived kanban boards from being resurrected #56030 validates the /events board query param against archived slugs.

Solution:
Reference #56030 and #43243 in the description so the dependency on the resurrection fix is visible, and scope the test plan's archive step to a gateway with the dispatcher stopped.

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Checked against 18e7a4c — the tip of fix/desktop-kanban-board-archive when this was written — and 6243136, main at the same moment.