There was no app-level notification surface: two components had grown
private toasts and the other 84 catch blocks ended at console.error,
so a user with a moved file, a locked database or an offline network
saw a button that did nothing. Where errors did surface, eight sites
printed the raw Go string.
Four levels, chosen by the call site from one rule — a failure is only
worth interrupting for if the user can do something about it that they
are not already doing: Blocking (data at risk), Persistent (something
asked for that did not happen, worth retrying), Transient (a small
action whose state visibly reverted anyway), Inline (rendered in the
panel that failed).
Three things about it are load-bearing. Coalescing lives in the store,
keyed by (level, region, key) within a window, so 200 unplayable files
are one message with a count and no future caller has to remember that.
An inline notification carries a *region*, because "inline" says not
global, not where. And the bottom band belongs to the player, so the
app-level stack sits under the header — the player's own floating
notice grows upward by however many lines it needs.
`utils/describe-error.ts` maps the causes a user can act on to copy;
`explainError` repeats a backend message when it is one of our own
sentinels rather than a Go wrapping chain, since mapping "a library
with that name already exists" to something generic is a regression.
`confirmAction()` is a wa-dialog, so destructive actions inherit the
focus trap and Escape the hand-rolled overlays do not have.
logan
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