docs(decisions): register Q-028 collision-resistant line IDs for auto-gen NPCs

NPC-scoped line ID scheme (D-035) works for hand-authored content but
will produce slug collisions with auto-generated populations (D-029).
Tracked as open question with ticket #544.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

decisions/questions.md

@@ -163,6 +163,14 @@ Tracked questions awaiting discussion or resolution.
 - **Assigned to:** Gestalt, Paula, Tyre
 - **Source:** Sprint 10 PR review discussion (2026-02-19)
 
+### Q-028: Collision-resistant line IDs for auto-generated NPCs
+- **Status:** Open
+- **Question:** The D-035 NPC-scoped line ID scheme uses NPC slugs as prefix (`kael-davan_d_001`). Hand-authored NPCs have unique slugs, but auto-generated populations (D-029: hundreds of NPCs) will produce collisions when the generator creates multiple NPCs with the same role slug (e.g., two `dock-worker` NPCs). What collision-resistance mechanism should be used? Options: (1) Short UUID/hash suffix on auto-gen slugs (`dock-worker-a7f3_d_001`), (2) Entity UUID as prefix, (3) Slug registry that guarantees uniqueness at generation time, (4) Composite key (entity ID + sequence) in server, human-readable slug only for authored content.
+- **Constraints:** Line IDs must be globally unique across entire save file lifetime (history log readiness). Must stay human-readable for hand-authored content. Server treats IDs as opaque strings — solution lives in content/generation layer. Must be compatible with D-035 NPC-scoped namespace.
+- **Ticket:** #544
+- **Assigned to:** Gestalt, Tyre
+- **Source:** Sprint 16 PR #59 review discussion (2026-02-23)
+
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-*27 questions (3 resolved, 2 partially resolved, 22 open). Last updated: 2026-02-19*
+*28 questions (3 resolved, 2 partially resolved, 23 open). Last updated: 2026-02-23*