fix: stop telling users to extract the release zip into a Unity project

The release notes now point at ~/.cursor/plugins/unity-developer-tools
and warn that extracting into a Unity project makes Unity compile the
snippets and templates. The Built-in-only surface shader moves to
snippets/shaders/legacy/ so it is not mistaken for a URP/HDRP sample.

Fixes #34

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MpEiWjv38TrdFcgqU8ER5L

Author: TMHSDigital

.github/workflows/release.yml

@@ -168,7 +168,7 @@ jobs:
 
             echo "---"
             echo ""
-            echo "**Install:** Download \`unity-developer-tools-v${{ steps.new.outputs.version }}.zip\` and extract into your project, or clone the repo and open in Cursor."
+            echo "**Install:** Extract \`unity-developer-tools-v${{ steps.new.outputs.version }}.zip\` into \`~/.cursor/plugins/unity-developer-tools\` (Windows: \`%USERPROFILE%\.cursor\plugins\unity-developer-tools\`), restart Cursor, then open your Unity project. Do not extract it into a Unity project: the snippets and templates are references, and Unity would compile them. See [Getting Started](https://github.com/${{ github.repository }}/blob/main/docs/GETTING-STARTED.md)."
             echo ""
             echo "**Full Changelog**: https://github.com/${{ github.repository }}/compare/${last_tag:-initial}...v${{ steps.new.outputs.version }}"
             echo "RELEASE_EOF"

README.md

@@ -198,7 +198,7 @@ Then ask the AI agent to scaffold a MonoBehaviour, look up an API, or generate a
 | `unlit-basic.shader` | Basic unlit shader for URP (HLSLPROGRAM) |
 | `urp-lit-template.shader` | PBR lit shader template for URP |
 | `hlsl-vertex-fragment.shader` | Custom vertex/fragment with URP lighting |
-| `surface-basic.shader` | Legacy surface shader (Built-in only) |
+| `legacy/surface-basic.shader` | Legacy surface shader (Built-in only; renders pink in URP/HDRP) |
 
 </details>