Install prepared original HUD caches and report resolved asset paths

docs/hud-installation.md

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+# Original HUD installation
+
+The runtime reads both caches from the selected `--assets` directory:
+
+| HUD | Default manifest | Optional development override |
+| --- | --- | --- |
+| Trick scoring | `private/hud/runtime/trickdisplay.json` | `SKATE_SCORING_HUD_ROOT` |
+| Session marker | `private/session-marker/hud.json` | `SKATE3_SESSION_MARKER_OVERLAY` |
+
+Merging HUD code does not install ignored, extracted game assets. Earlier feature
+launchers used private caches through environment overrides; the combined build
+with only `--assets` could not find either cache. Setup now prepares both with
+the existing extractors. The marker extractor defaults to the vendored UI toolkit;
+the external `--ui-toolkit` argument remains supported.
+
+For an existing installation, reuse prepared caches without reconverting maps:
+
+```powershell
+python tools/install_prepared_hud.py --assets <installed-assets> --scoring-cache <prepared-scoring-cache> --marker-cache <prepared-marker-overlay>
+```
+
+This validates both manifests and referenced texture sizes before copying any
+files, checks available marker texture hashes, and verifies byte-identical copies.
+It refuses differing installed files unless `--replace` is supplied. It installs
+only the runtime files, preserving authored geometry, fonts, images and actions.
+No copyrighted assets are committed or bundled with the source.
+
+If no prepared caches exist, prepare only the two HUDs from the owned game folder:
+
+```powershell
+python tools/prepare_hud.py --game <owned-game> --output <installed-assets>/private/hud --collections <installed-assets>/private/stock/skater-collections.json
+python tools/extract_session_marker.py --game <owned-game> --output <installed-assets>/private/session-marker
+```
+
+Startup logs report the loaded paths or a load failure. Check the executable and
+asset paths in the launcher as well: `PLAY.bat` delegates to `Launch.ps1`, which
+selects `bin/skate3rust.exe`, not a feature build elsewhere in `bin`.
+
+Session-marker prompts appear while holding LB during gameplay; they are not an
+always-visible panel. Scoring follows the original trickdisplay movie. Its camera
+renders layer 31 offscreen before the presentation UI; the marker camera renders
+layer 29 at order 1 after presentation. The existing scoring startup dependency
+on `PresentationSetup` must be retained. Neither HUD uses the world mesh layers.
+
+The installation repair and release compilation do not establish GPU visibility
+or gameplay parity. Manual checks remain: resume gameplay, hold LB for the marker
+panel, and perform and land a trick for the scoring display.