docs: record the Slice 0.9 quest system and its deviations

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/playable-slices/0.9-First-Quest-and-Bag-Tutorial.md

@@ -314,9 +314,85 @@ Hide Capacity: 5
 - [ ] Quest grants no XP.
 - [ ] All dialogue/UI text is English.
 
+### Verification status
+
+Every criterion above is covered by automated tests: the quest chain in
+`quest-state.spec.ts` and `quest.service.spec.ts`, the content in
+`vertical-slice.seed.spec.ts`, the markers in `npc.service.spec.ts`, and the
+three UI requirements of §12 in the web specs for the journal, the NPC screen
+and the location hotspots.
+
+The boxes stay unticked because two things have not been run: the migration and
+seed against a real PostgreSQL database, and a hand-played pass through the
+chain in the running app. Neither was possible in the environment this slice was
+built in — no database was reachable. Do both before ticking, following the
+walkthrough in the implementation plan
+(`docs/superpowers/plans/2026-08-22-first-quest-and-bag-tutorial.md`, Task 13).
+
 ---
 
-## 15. Out of Scope
+## 15. Implementation Decisions
+
+Recorded here rather than only in the implementation plan, so the next slice
+reads them from the specification.
+
+### D1 — The Basic Hide Bag is granted, not sold
+
+§6 has Borin say "Take this" while also describing the Slice 0.8.5 offer, which
+costs 35 Silver. A player standing at that step has close to none, so the
+purchase path alone would stall the chain.
+
+Borin's quest step therefore hands the bag over directly and idempotently. The
+referral flag is still written to the character's Borin state, so the 0.8.5
+`bypassConditions` gate opens the offer as well — a visible consequence, and a
+way back to a bag that is somehow lost. Nothing about reputation changes.
+
+### D2 — No World Renown milestone
+
+§9 lists one as optional. The demo character sits at Renown 1 and the first
+trade-in takes them to 2; a quest milestone would reach 3 and unlock Borin's
+Bandit Blade, which Slice 0.8.5 deliberately placed out of reach until Slice
+0.11. The quest pays regional reputation instead: **+10 Border Watch**.
+
+### D3 — No Silver reward
+
+§9 warns against a Silver reward that undermines the merchant trade loop, and
+names the bag and system knowledge as the point of the chain. `rewardSilver` is
+a content column set to 0, so retuning it later is a seed change.
+
+### D4 — Quest steps use their own endpoints
+
+NPC spec §40 asked Slice 0.9 to also wire the `START_QUEST` / `COMPLETE_QUEST`
+dialogue actions. There is no dialogue-response endpoint at all, and building
+one plus an action executor is the branching narrative engine §10 rules out.
+
+Steps run through `POST /api/npcs/:npcKey/quests/:questKey/{accept,advance}`.
+Neither takes a body — which step is current, what it grants and what it
+consumes are the server's to decide. The line an NPC speaks for a step is
+content on the objective. Recorded as Abweichung 4 in the NPC specification.
+
+### D5 — The demo character starts with no loot bag
+
+The vertical-slice seed handed over a free Basic Hide Bag as a stopgap between
+Slices 0.8.5 and 0.9, with a note to remove it once a quest could grant one.
+That is done: the bagless HIDE capacity of 1 is the whole premise of §4. The
+migration also clears that one row for the demo character on databases seeded
+before this change.
+
+### Addition — a hint for the second pelt hunt
+
+Not in the specification, but the same courtesy §4 asks for. The Hide Bag holds
+five of *any* hide, so Tough Hides can crowd out the fifth Ashen Pelt. That step
+must not give up the way the first one does — it is meant to be finished (§7) —
+so it carries a hint instead:
+
+```text
+Your hide bag is full of other goods. Trade some to Borin to make room for pelts.
+```
+
+---
+
+## 16. Out of Scope
 
 Do not implement: