Builds on @nductien's completion-notify module (PR #87705):
- Notify on the gateway watcher's full terminal set — blocked, gave_up,
crashed, timed_out, block_loop_detected — not just completed. A worker
hitting a blocker while the user is away was the original community ask.
- Route all notification copy through the kanban plugin i18n bundles
(en/ja/zh/zh-hant), with an English-bundle fallback when the translator
isn't bound yet.
- Wire the ctx.os.notify door so events also fire a NATIVE OS notification
while the user is away from the Hermes window (host.notify toast covers
the foreground). OS-door failures are isolated from the toast path.
- Docs: Desktop notifications section in kanban.md, including the
app-running coverage window.
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