Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

RTL (GS rasterizer, EE core stub, platform bridge, LPDDR4B path), sim regression
(272 TBs), docs, and tooling. Copyrighted PS2 content (BIOS, game code, GS dumps,
and all dump-derived textures/traces) is excluded via .gitignore and stays local.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

references/README.md

@@ -0,0 +1,36 @@
+# PS2 Reference Notes
+
+This folder is a planning-oriented reference bundle for the `retroDE_ps2`
+core. It is not meant to be an exhaustive PS2 encyclopedia; it is meant to
+collect the implementation details that are likely to matter when we turn this
+into an FPGA project.
+
+Files in this folder:
+
+- `hardware_overview.md`: PS2 subsystem map, memory map, and boot flow notes.
+- `software_and_emulators.md`: Open-source SDK, graphics libraries, and
+  emulator projects worth mining for behavior and test ideas.
+- `implementation_workstreams.md`: A subsystem-by-subsystem map of what the
+  project would need to account for, plus an `ao486` comparison.
+- `source_log.md`: Source list with URLs and short notes.
+- `supplemental/`: Second-pass additions (Claude). Primary Sony manuals,
+  PSX-on-FPGA prior art as methodology templates, academic / community
+  feasibility material. See `supplemental/README.md`.
+
+Suggested reading order:
+
+1. `hardware_overview.md`
+2. `implementation_workstreams.md`
+3. `software_and_emulators.md`
+
+Notes:
+
+- These notes favor primary or near-primary technical sources where possible:
+  emulator source trees, SDK/toolchain repos, and low-level hardware
+  references.
+- Some PS2 knowledge still lives in community documentation rather than
+  official Sony publications. Where that is the case, the source is called out
+  clearly.
+- I did not find a credible open-source HDL PS2 core during this pass. The
+  public material that surfaced is overwhelmingly emulator, homebrew SDK, and
+  reverse-engineering documentation.