The action lifecycle (Idle | Busy | Failed) lived in an imperative
store-level signal, set from ten call sites outside the reducer. The
reducer could not enforce which action transitions are legal.
Add `action` to `BriefState.Loaded`, driven by three new messages
(ActionStarted, ActionFinished, ActionFailed) and handled in `reduce`.
Replace every `actionState.set(...)` call in `brief.store.ts` with the
matching `dispatch`. `BriefLoaded` resets `action` to Idle, so a fresh
load clears a stale action error instead of letting it outlive the
reload.
`busy` and `lastError` stay as `computed`s on the store with a
byte-identical public signature — they are the render seam for four
components and two page templates, and the union belongs in the
machine, not the components. `revealBigNummer` still sets only
`Failed`, never `Busy` — an existing asymmetry, not changed here.
`SaveState`, `org-template.store.ts`, and `pendingPublish` are out of
scope (RD-13, RD-14).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
