qa: make the demo walkable — terrain collision root cause, spawn, scripted QA

The reported fall-through was a misdiagnosis: the player never fell. The
imported Terrain_DEM had only a bounding-box simple collision proxy, so a
downward trace anywhere in the block hit the terrain at Z 819 (the mesh
bbox max) and the street sat under an invisible 8 m lid. Standing on that
box looked plausible, which is why it read as working.

- add UGigLineAssetTools (C++): force CTF_UseComplexAsSimple on a static
  mesh. UE 5.8 dropped bUseComplexAsSimpleCollision and Python cannot set
  the flag; the builder also saves the asset, since the flag lives there
  and a map-only save silently reverts it.
- spawn (-13336, -1150, 600): inside the carved corridor (the cut is a
  10.7 m half-width around the road centreline), lands on the road at 456.
- fix ResetToStart returning to the mid-air PlayerStart captured in
  BeginPlay: StartLocation is now captured on the first grounded frame.
- HighResShot 1280x720 instead of "1280 720", which is a multiplier.
- add -qaselftest: scripted walk/reset/pause on a core ticker plus a
  swept ground transect. Results: walk 746 cm/2 s with Z steady, reset
  0 cm from spawn, pause/unpause 1/0, transect 84 samples 0 holes.
- rebase onto main, keeping the frontage materials and placement fixes.

MEMORY.md

@@ -6,6 +6,22 @@ Scope: facts and traps that cost time to establish. Planned work lives in [TODO.
 
 ---
 
+## 2026-11-08 — Reset was returning to mid-air; QA self-test switch
+
+- **`ResetToStart()` restored a `StartLocation` captured in `BeginPlay`**, which is the PlayerStart position *above* grade (Z 600) so the capsule never spawns embedded. Every reset therefore dropped the player 1.4 m back into the air. Fix: capture `StartLocation` on the first grounded frame (repeating 0.25 s timer, cleared once captured) — not a one-shot timer, which can fire after the player has already started walking and record a mid-stride position.
+- **`-qaselftest`** drives the checks headlessly and logs `GigLine QA: ... PASS/FAIL`. It runs on a **core ticker, not a world timer**: pausing the game stops world timers, so a timer-driven test freezes exactly when it proves pause works.
+- Current results: walk 746 cm / 2 s with Z steady, reset 0 cm from spawn, pause `IsGamePaused()` 1, unpause 0, transect 84 samples / 0 holes (ground Z 317..395).
+
+## 2026-11-08 — The fall-through was an 8 m invisible box (QA branch)
+
+- **Symptom:** player "spawned above ground but never fell", sat at Z 909, `fall=0`, `mode=1` (Walking), no fall-through, view looked plausible so it was mistaken for working.
+- **Cause:** `Terrain_DEM` had only a **bounding-box simple collision proxy** (Interchange default). A line trace down at *every* Y through the block hit `Demo_Terrain_DEM` at exactly **819** — the mesh bbox max Z. The whole street was under an invisible lid; the pawn stood on the box, 8 m above the road.
+- **Proof:** a debug `LineTraceSingleByChannel` profile at Y −1912…+1447 reported `top=819 actor=Demo_Terrain_DEM` for the entire street. After the fix it reports `Sidewalk_North 395`, `Road_Hollywood 366`, `Sidewalk_South 317`.
+- **Fix:** force complex-as-simple collision on the terrain. Python **cannot** set it (`StaticMesh`/`BodySetup` expose no such property; `dir()` shows only `lod_for_collision`). Added `UGigLineAssetTools::SetComplexCollisionAsSimple` in the C++ module (`BodySetup->CollisionTraceFlag = CTF_UseComplexAsSimple`, UE 5.8 no longer has `bUseComplexAsSimpleCollision`).
+- **Second gotcha:** the flag lives on the **asset**, not the map. Setting it in a builder session and saving only the `.umap` loses it — `EditorAssetLibrary.save_loaded_asset()` is required, otherwise the next run reloads the bbox proxy.
+- **Third gotcha:** `HighResShot 1280 720` means **multiplier 1280** (UE warns "the high resolution screenshot multiplier is too large for your system"). The correct form is `HighResShot 1280x720`.
+- Resulting spawn: `(-13336, -1150, 600)` — inside the carved corridor, lands on the road at Z 456 (feet 368 on road top 366).
+
 ## 2026-11-07 — Publication audit
 
 - MPFB 2.0.18's installed `blender_manifest.toml` identifies its code as GPL-3.0-or-later; its versioned `LICENSE.md` explicitly puts bundled mesh, texture, and rig assets under CC0 1.0. The earlier CC0 claim for the add-on code was wrong.
@@ -199,3 +215,24 @@ 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).