memory: document walkable demo QA root causes (default map, input cook, collision)

MEMORY.md

@@ -199,3 +199,24 @@ Scope: facts and traps that cost time to establish. Planned work lives in [TODO.
 - The two north-side buildings (TCL, Tussaud's) were similarly on the **south** side: `export_north_buildings.py` mirrored Y, which put them where the frontage belongs.
 - Fix: hero at X −13336 / Y +1307 (the frontage gap between 6902 and 6838); frontage and north buildings exported **without** a Y mirror (the FBX preset already maps Blender −Y south to UE +Y south).
 - Lesson: **place a building only against a neighbour or the street mesh, never in isolation.** A single object in an empty map hides any number of placement errors; adding the adjacent frontage immediately exposed this one.
+## 2026-11-07 — walkable demo QA bugs (fix branch qa-input-collision-fix-0.1.0)
+
+- **"Stuck" window = wrong default map.** A plain `./GigLine.sh` opened
+  `/Engine/Maps/Templates/OpenWorld` (empty engine template) instead of the demo,
+  so nothing was interactive. `GameDefaultMap` was in `DefaultGame.ini` and not
+  applied; it must live in `DefaultEngine.ini[/Script/EngineSettings.GameMapsSettings]`
+  with `GlobalDefaultGameMode`. Verified: plain launch now loads
+  `/Game/Hollywood/DemoMap`. Evidence: `LogLoad: LoadMap: /Engine/Maps/Templates/OpenWorld`.
+- **Input assets were pruned from the pak.** The Enhanced Input assets under
+  `/Game/Input` were only soft-referenced at runtime, so the cooker excluded them
+  (cook `ReferencedSet.txt` had zero `/Game/Input` lines -> all inputs nil at
+  runtime). Fix: hard-reference via `ConstructorHelpers::FObjectFinder` in the
+  character ctor (cooker follows hard refs) + `+DirectoriesToAlwaysCook`. Packaged
+  log then showed `ctx=ok move=ok ... jump=ok`.
+- **Character fell through** the site: site meshes staged MOVABLE + PlayerStart far
+  past the north sidewalk. Fix: STATIC mobility + explicit collision
+  (QUERY_AND_PHYSICS/WorldStatic/BlockAll) and PlayerStart at Y -1200 on the
+  sidewalk. Packaged run: `grounded=1 movement=Walking`.
+- Diagnose packaged runtime via the engine log
+  (`.../Linux/GigLine/Saved/Logs/GigLine.log`); a headless `-nullrhi` commandlet
+  cannot validate physics traces (even a spawned cube returns NO HIT there).