chore: phase 0 — skeleton + dat asset inventory

Brand-new solution targeting .NET 10, using Chorizite.DatReaderWriter 2.1.4
to walk a retail AC dat directory and print how many of each asset type live
in client_portal / client_cell_1 / client_highres / client_local_English.

Opens the four dats in ~16 ms and counts 887,381 indexed assets across 40+
tracked DBObj types. Cell-database terrain (LandBlock, LandBlockInfo, EnvCell)
uses mask-based IDs that DatReaderWriter 2.1.4's GetAllIdsOfType<T> does not
support; worked around with a manual b-tree walk in CountCellByLow16.

Sanity check: LandBlock count is 65,025 = 255 x 255, exactly the AC world grid.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -0,0 +1,22 @@
+# acdream
+
+Experimental modern open-source Asheron's Call client in C# / .NET 10.
+
+**Status:** pre-alpha, not playable. Phase 0 only — dat file asset inventory.
+
+**Stack:** .NET 10, [Chorizite.DatReaderWriter](https://github.com/Chorizite/DatReaderWriter) for dat parsing. Silk.NET + Avalonia planned for rendering/UI (not yet wired up).
+
+**Requires:** A retail Asheron's Call install (Turbine/Microsoft property — supply your own). Set `ACDREAM_DAT_DIR` environment variable to the directory containing `client_portal.dat`, `client_cell_1.dat`, `client_highres.dat`, and `client_local_English.dat`, or pass it as the first CLI argument.
+
+## Layout
+
+- `src/AcDream.Cli/` — console app that dumps asset counts from a dat directory
+- `references/` — local read-only reference material (ACE, ACViewer, WorldBuilder, DatReaderWriter, holtburger, retail AC install). Gitignored.
+
+## Run
+
+```
+dotnet run --project src/AcDream.Cli -- "C:\path\to\Asheron's Call"
+```
+
+Or set `ACDREAM_DAT_DIR` and run without args.