…rsioned git URLs

Unity doesn't update users who install with a fixed version

- Remove sed commands that update version references in README.md and README-zh.md
- Update git add command to exclude README files from version bump commits
- Change README installation URLs from versioned (#v8.1.0) to unversioned (no tag)
- Add documentation showing how to use tagged URLs for users who need fixed versions

* Standardize import ordering and whitespace in plugin

The whitespace gave a warning in the asset store submission

* Fix manage_prefab tool structure

* Fix manage_editor actions

* Add get_component singular to manage_gameobject

* Improve uv cache clear error handling with lock detection and combined output

Replace simple stderr-only error reporting with combined stdout/stderr output. Add detection for "currently in-use" lock errors with helpful hint about waiting or using --force flag. Provide fallback message when command fails with no output.

* Improve error message formatting in uv cache clear failure logging

Update mcp-for-unity script entry point from "main:main" to "src.main:main" to match the actual module structure after moving main.py into the src directory.