docs: change README installation examples from fixed version to beta branch

Remove version-specific installation examples from README.md and README-zh.md, replacing with beta branch references. Update release workflow and update_versions.py to stop modifying README files during version bumps since they no longer contain version-specific URLs.

.github/workflows/release.yml

@@ -107,7 +107,7 @@ jobs:
           git config user.name "GitHub Actions"
           git config user.email "actions@github.com"
           git checkout -b "$BRANCH"
-          git add MCPForUnity/package.json manifest.json "Server/pyproject.toml" Server/README.md README.md docs/i18n/README-zh.md
+          git add MCPForUnity/package.json manifest.json "Server/pyproject.toml" Server/README.md
           if git diff --cached --quiet; then
             echo "No version changes to commit."
           else

README.md

@@ -36,9 +36,9 @@ In Unity: `Window > Package Manager > + > Add package from git URL...`
 > https://github.com/CoplayDev/unity-mcp.git?path=/MCPForUnity
 > ```
 
-**Need a stable/fixed version?** Use a tagged URL (requires uninstall to update):
+**Want the latest beta?** Use the beta branch:
 ```text
-https://github.com/CoplayDev/unity-mcp.git?path=/MCPForUnity#v9.1.0
+https://github.com/CoplayDev/unity-mcp.git?path=/MCPForUnity#beta
 ```
 
 <details>

docs/i18n/README-zh.md

@@ -36,9 +36,9 @@
 > https://github.com/CoplayDev/unity-mcp.git?path=/MCPForUnity
 > ```
 
-**需要一个稳定/固定版本？** 使用带 tag 的 URL（更新时需要卸载才能更新）：
+**想要最新的 beta 版本？** 使用 beta 分支：
 ```text
-https://github.com/CoplayDev/unity-mcp.git?path=/MCPForUnity#v9.1.0
+https://github.com/CoplayDev/unity-mcp.git?path=/MCPForUnity#beta
 ```
 
 <details>

tools/update_versions.py

@@ -265,11 +265,6 @@ def main() -> int:
         if update_server_readme(version, args.dry_run):
             updates_made.append("Server/README.md")
 
-        if update_root_readme(version, args.dry_run):
-            updates_made.append("README.md")
-
-        if update_zh_readme(version, args.dry_run):
-            updates_made.append("docs/i18n/README-zh.md")
 
         # Summary
         if args.dry_run: