test: add issue 278 locale and audio smoke gate

docs/ISSUE-278-SMOKE-E2E-GATE-ARTIFACT.md

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+# Issue #278 Artifact — smoke/e2e gate for da+en locale flow and primary-only audio
+
+## Scope
+Acceptance for `[READY][#175][P4]`:
+1. Verify one MVP host+player smoke run in `en`.
+2. Verify one MVP host+player smoke run in `da`.
+3. Verify audio routing remains `primary-device only` so phone/player clients never take playback ownership.
+
+Dette er en gate-/evidensleverance. Ingen ny produktfunktion ud over test/verifikation.
+
+## Implemented smoke gate
+Angular smoke spec: `frontend/angular/src/app/i18n-mvp-flow-smoke.spec.ts`
+
+The gate now runs two explicit locale scenarios:
+- `en`: host refresh/start-round copy + player submit-guess copy
+- `da`: samme flow med dansk copy
+
+Audio-policy delen af samme smoke-spec verificerer:
+- host/primary playback path er uændret før player mount
+- player mount installerer no-audio guard på secondary device
+- guard fjernes igen ved unmount, så primary path fortsat er eneste aktive output
+
+## Recommended verification command
+Køres fra `frontend/angular`:
+
+```bash
+npm test -- --run src/app/i18n-mvp-flow-smoke.spec.ts src/app/lobby-i18n.spec.ts src/app/features/player/player-shell.component.spec.ts
+```
+
+## Why this is the gate
+- `i18n-mvp-flow-smoke.spec.ts` giver en lille, samlet smoke/e2e-lignende verifikation af host+player i begge locale-kontekster.
+- `lobby-i18n.spec.ts` holder shared locale propagation + contract fallback grøn.
+- `player-shell.component.spec.ts` dækker den dybere regressionflade for audio-guard på secondary device.
+
+## Conclusion
+Gate’en verificerer nu eksplicit begge locale-runs (`da` + `en`) og bekræfter primary-only audio routing i MVP-flowet.