fix(input): restore working controls + add input harness + build fixes

Consolidated from the qa-input-collision-fix-0.1.0 work, applied onto main so
only the changes main genuinely lacks are carried (main already merged the
walkable-demo/collision work independently).

- fix(input): populate the UE 5.8 FInputMappingContextMappingData
  DefaultKeyMappings field in ue_create_input_assets.py (the runtime reads
  GetMappings()->DefaultKeyMappings.Mappings; the script previously wrote only
  the deprecated 'mappings' array, so the cooked game had 0 runtime mappings
  and every key silently did nothing — in packaged AND PIE). Regenerated
  IMC_Default.uasset. WASD/mouse/Space/R/Escape verified working.
- fix(build): drop editor-only APIs that break the game target build —
  UStaticMesh::PostEditChange() (GigLineAssetTools) and AActor::GetActorLabel()
  (character ground probe). GigLine and GigLineEditor now both compile clean.
- tools: OS-level uinput input harness (input_emulation.py + input_test.py) and
  run_pie.sh for PIE isolation; document the PIE-vs-packaged input test in
  Docs/build.md. Removed the temporary SIM/EI/screenshot diagnostics from the
  character.

Docs/build.md

@@ -10,7 +10,8 @@ Fresh-checkout build procedure. Completed 2026-11-07 after the pinned engine was
 
 ## Engine
 
-Pinned install: **Unreal Engine 5.8.4** (CL 58902052, promoted build) at `/run/media/system/DATA/Engines/UE_5.8.4`. The engine bundles **no** Linux clang; the system clang (23.1.4, Fedora 45) is the game-code toolchain. Game targets must use `BuildSettingsVersion.V7` to share the installed editor's build environment.
+Pinned install: **Unreal Engine 5.8.4** (CL 58902052, promoted build) at
+`/run/media/system/DATA/Engines/UE_5.8.4`. The engine bundles **no** Linux clang; the system clang (23.1.4, Fedora 45) is the game-code toolchain. Game targets must use `BuildSettingsVersion.V7` to share the installed editor's build environment.
 
 ## Fresh-checkout build
 
@@ -48,7 +49,13 @@ Engine/Build/BatchFiles/RunUAT.sh BuildCookRun \
 # Launch test (plain, no -map): /run/media/system/DATA/Builds/GigLine/Linux/GigLine.sh
 ```
 
-**Launch test must open the DemoMap.** A plain `./GigLine.sh` should load `/Game/Hollywood/DemoMap` (set via `DefaultEngine.ini` `GameMapsSettings`). If it instead opens `/Engine/Maps/Templates/OpenWorld`, the game shows an empty non-interactive "stuck" scene — check that `GameDefaultMap` is in `DefaultEngine.ini`, not `DefaultGame.ini`. Confirm the loaded map in the engine log: `.../Linux/GigLine/Saved/Logs/GigLine.log` (`LoadMap: /Game/Hollywood/DemoMap`). The archive directory is deliberately **outside** the repository; never archive into the checkout.
+**Launch test must open the DemoMap.** A plain `./GigLine.sh` should load
+`/Game/Hollywood/DemoMap` (set via `DefaultEngine.ini` `GameMapsSettings`). If it
+instead opens `/Engine/Maps/Templates/OpenWorld`, the game shows an empty
+non-interactive "stuck" scene — check that `GameDefaultMap` is in
+`DefaultEngine.ini`, not `DefaultGame.ini`. Confirm the loaded map in the engine
+log: `.../Linux/GigLine/Saved/Logs/GigLine.log` (`LoadMap: /Game/Hollywood/DemoMap`).
+The archive directory is deliberately **outside** the repository; never archive into the checkout.
 
 ## Headless content checks
 
@@ -69,7 +76,9 @@ Both content-acceptance tests run headless and are the template for all asset im
 
 ## Content pipeline (current)
 
-The hero block and the demo level are built by a fixed sequence. Each step writes a result file under `/tmp/gigline/`; read it, because the commandlet's own stdout can be swallowed.
+The hero block and the demo level are built by a fixed sequence. Each step writes
+a result file under `/tmp/gigline/`; read it, because the commandlet's own stdout
+can be swallowed.
 
 | Step | Tool | Output |
 | --- | --- | --- |
@@ -86,8 +95,12 @@ The hero block and the demo level are built by a fixed sequence. Each step write
 
 Two rules that the pipeline enforces rather than documents:
 
-- **One conversion.** Metres to Unreal centimetres happens only in `Geo/tools/osm_common.py::to_unreal_local`. Sidecars (`<asset>.geo.json`) record the result and `Geo/tools/asset_metadata.py audit` re-derives it.
-- **Collision is decided at import,** not later: terrain, road and sidewalks are complex-as-simple; kerbs and props stay simple. A simple hull over a kerbed street ramps straight across the kerb.
+- **One conversion.** Metres to Unreal centimetres happens only in
+  `Geo/tools/osm_common.py::to_unreal_local`. Sidecars (`<asset>.geo.json`) record
+  the result and `Geo/tools/asset_metadata.py audit` re-derives it.
+- **Collision is decided at import,** not later: terrain, road and sidewalks are
+  complex-as-simple; kerbs and props stay simple. A simple hull over a kerbed
+  street ramps straight across the kerb.
 
 ## Known engine quirks (2026-11-07)
 
@@ -98,3 +111,19 @@ Two rules that the pipeline enforces rather than documents:
 ## Packaged Linux build
 
 - 2026-11-07: blank `Game/GigLine` Development build packaged via the command above; 1.1 GiB archive at `/run/media/system/DATA/Builds/GigLine/Linux`; `GigLine.sh` launched on the desktop session, Vulkan swapchain created, 759 frames rendered across a 60 s smoke test. Controls document to be written with the first playable (`0.1.0` Gameplay section).
+
+## PIE input test (compare editor vs packaged input intake)
+
+Use to isolate whether the "no controls respond" bug is the packaged standalone's
+input intake or the Enhanced Input wiring generally.
+
+- `Tools/run_pie.sh` opens the editor on `/Game/Hollywood/DemoMap`. Press the
+  green **Play** (PIE) button and walk / mouse-look.
+- Interpretation:
+  - PIE **works** -> the Enhanced Input wiring is fine and the standalone
+    packaged build's SDL input intake is the environment-dependent bug.
+  - PIE **fails** too -> the Enhanced Input setup itself is broken; rebuild
+    the input config / character from scratch.
+- The DemoMap is PIE-ready as committed: `GlobalDefaultGameMode` +
+  `GameDefaultMap=/Game/Hollywood/DemoMap`, and the map stages a PlayerStart at
+  `(-13336,-1150,600)` on the cut sidewalk with the walkable `AGigLineCharacter`.