feat(windows): keep dwm shadow on frameless windows

[chen-zeong]

Fixes #13134.

Summary

• keep the native DWM shadow when Windows decorations are disabled so frameless windows stay resizable
• store the shadow preference on WindowWrapper and drive it from SetShadow/SetDecorations handlers
• add a dedicated shadow helper to toggle and reset DWM attributes

Testing

• set decorations: false and shadow: true in examples/helloworld/tauri.conf.json
• cargo run --example helloworld (Windows 10) and verify the window stays frameless, keeps its shadow, and remains resizable from every edge

[github-actions]

Package Changes Through b5cefdc

There are 10 changes which include @tauri-apps/api with minor, tauri-cli with minor, tauri-utils with minor, tauri-runtime-wry with minor, tauri-runtime with minor, tauri with minor, tauri-bundler with minor, @tauri-apps/cli with minor, tauri-codegen with patch, tauri-macros with patch

Planned Package Versions

The following package releases are the planned based on the context of changes in this pull request.

package	current	next
@tauri-apps/api	2.8.0	2.9.0
tauri-utils	2.7.0	2.8.0
tauri-bundler	2.6.1	2.7.0
tauri-runtime	2.8.0	2.9.0
tauri-runtime-wry	2.8.1	2.9.0
tauri-codegen	2.4.0	2.4.1
tauri-macros	2.4.0	2.4.1
tauri-plugin	2.4.0	2.4.1
tauri-build	2.4.1	2.4.2
tauri	2.8.5	2.9.0
@tauri-apps/cli	2.8.4	2.9.0
tauri-cli	2.8.4	2.9.0

Add another change file through the GitHub UI by following this link.

---

Read about change files or the docs at github.com/jbolda/covector

[chen-zeong]

or add a frameless parameter, regardless of whether the decorations are false, can set no border, this is the code