docs: add staging gameplay smoke evidence artifact template (#144)

docs/STAGING_GAMEPLAY_SMOKE_ARTIFACT.md

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+# Staging gameplay smoke artifact (Issue #144)
+
+Formål: levere et lille, ensartet evidensformat for release-nær gameplay-smoke i #16/#90-sporet uden scope-udvidelse.
+
+## Guardrails (MVP)
+- Hold scope inden for #16 (execution board) og #17 (scope guardrail).
+- Kun verifikation af eksisterende flow; ingen nye features/polish.
+
+## Hvornår bruges artifacten
+- Efter staging-smoke af gameplay-flowet: lobby -> join -> start -> runde -> scoreboard -> next/final.
+- Resultatet logges i issue/PR-kommentar med denne skabelon.
+
+## Evidence template (kopiér i PR/issue-kommentar)
+```markdown
+### Staging gameplay smoke evidence
+- Timestamp (UTC): <YYYY-MM-DD HH:MM>
+- Environment: staging
+- Commit/Head SHA: <sha>
+- Linked scope: #16 #17 #90 #129 #144
+
+#### Setup
+- Host authenticated in Django admin: <yes/no>
+- Active category/questions present: <yes/no>
+- Participants: host + <N> players
+
+#### Checks (PASS/FAIL)
+1. Lobby -> join -> start
+   - Mixed-case + whitespace session code accepted: <pass/fail>
+2. One full round to scoreboard
+   - submit lie -> mix -> submit guess -> calculate score -> show scoreboard: <pass/fail>
+3. Next-round + game-end sanity
+   - next round transitions: <pass/fail>
+   - final leaderboard visible: <pass/fail>
+
+#### Evidence pointers
+- Command(s): `<exact command(s)>`
+- UI notes/screenshots/log refs: <short refs>
+- Result: <PASS/FAIL>
+- If FAIL: blocker issue link + shortest repro
+```
+
+## Anti-stall minimum
+Hvis der ikke er ny kode at ændre, er denne artifact-skabelon den mindste gyldige leverance for at sikre ensartet, reviewbar smoke-evidens i staging.