Prepare repository for public release

- README: attract-mode stills + demo GIF as the hero row, status/warning
  callouts, metrics table, "Contents" index, doc-index table; simplified
  the two-agent workflow diagram (LR -> TD, fewer edges) for GitHub web
- Table-of-contents indexes added to internals.md, porting-notes.md,
  agentic-development.md, AUDIO-PLAN.md
- CI: add Windows/MSYS2 build job, minimal token (contents: read),
  persist-credentials: false, concurrency group; run on main + master.
  validate job regenerates the US ROM-asset symbol file only and configures
  ntsc-final (PAL/JP need a region ROM; no ROM is used in CI)
- .github: SECURITY.md, issue forms + chooser config, PR template,
  labels.yml, dependabot (Actions, monthly)
- Do not track the proprietary SGI IRIX IDO toolchain or SGIImageViewer.exe;
  document in SetupGuide.md / building.md how to obtain IDO for N64 ROM
  builds (the PC port does not need it)
- Stop tracking two committed *.pyc files; drop stale screenshots and a
  redundant .gitignore line; misc doc cross-reference fixes

Claude-Session: https://claude.ai/code/session_01GULf6knbsqfsnW39tMr9WT

docs/internals.md

@@ -17,6 +17,27 @@ platforms.
 
 ---
 
+## Contents
+
+1. [Executive summary](#1-executive-summary)
+2. [What the PD port actually does (the reference architecture)](#2-what-the-pd-port-actually-does-the-reference-architecture)
+   — [2.1 Emulate the RSP, bypass the RDP](#21-the-key-architectural-insight-emulate-the-rsp-bypass-the-rdp)
+   · [2.2 How the RSP is invoked](#22-how-the-rsp-is-invoked)
+   · [2.3 Build system](#23-build-system)
+   · [2.4 PD-port copy-candidate audit](#24-pd-port-copy-candidate-audit-session-2026-08-22)
+3. [GoldenEye decomp: what we're porting](#3-goldeneye-decomp-what-were-porting)
+   — [3.1 Entry / main loop](#31-entry--main-loop)
+   · [3.2 The two libultra trees](#32-the-two-libultra-trees-srclibultra-and-srclibultrare)
+4. [N64 hardware surfaces that must be shimmed](#4-n64-hardware-surfaces-that-must-be-shimmed)
+5. [GE-specific graphics differences vs PD (the RSP work)](#5-ge-specific-graphics-differences-vs-pd-the-rsp-work)
+6. [Audio](#6-audio)
+7. [Input & saves](#7-input--saves)
+8. [Recommended plan](#8-recommended-plan) — phases 0–4
+9. [Open questions / risks](#9-open-questions--risks)
+10. [References](#10-references)
+
+---
+
 ## 1. Executive summary
 
 * **Feasibility: HIGH.** GoldenEye and Perfect Dark share the same Rare