Prepare v0.5.0 release

[asklar]

Summary

Prepare the v0.5.0 release by bumping the repository's single authoritative product VERSION from 0.4.0 to 0.5.0.

This one file feeds:

• CMake PROJECT_VERSION and lvt --version
• Win32 VERSIONINFO resources for native EXEs/DLLs
• MSBuild assembly/file/informational versions for the Viewer and managed tree walkers
• The MCP server's reported lvt product version through lvt_api_version()

mcp/Cargo.toml remains decorative metadata for a non-published static library, and plugin.json independently versions the Copilot skill bundle.

Release highlights since v0.4.0

New features

• Add lvt Viewer, a live graphical visual/UIA tree browser with Inspect-style crosshair targeting, element highlighting, filtering, search, live updates, and UIA Toggle/Value editing.
• Publish the viewer as a separate, version-matched lvt-viewer-v0.5.0-x64.zip, including the complete matching x64 lvt runtime while keeping normal CLI archives lean.
• Add persistent XAML/WinUI3 and UIA connections for long-running watch and MCP sessions, avoiding per-refresh reinjection/client recreation.
• Add incremental XAML change delivery and robust cross-tick tree reconciliation.
• Add --fast XAML/WinUI3 collection for rich trees.
• Add compact xaml:0x... / winui3:0x... element keys.
• Add plugin ABI v2 for optional persistent provider connections.
• Support system-XAML desktop islands such as Windows Terminal and distinguish WinUI 2 from WinUI 3 correctly.

Bug fixes

• Correct XAML property handling for legitimate zero-valued enums and long numeric strings.
• Preserve WPF Hidden vs. Collapsed, zero-size state, and empty text semantics.
• Fix persistent connection recovery, first-connect retries, stale viewer process-exit races, and full-tree reset behavior.
• Fix viewer crosshair hit testing, highlight occlusion/z-order behavior, Unicode decoding, and private-use glyph display.
• Remove redundant initial XAML collection and prevent per-tick TAP property accumulation/stale fast-mode bounds.
• Harden concurrent MCP disconnect and plugin persistent-connection lifetime contracts.
• Repair installed public headers and multi-architecture release packaging.

Verification

• Native CLI reports lvt 0.5.0.
• Native file/product VERSIONINFO reports 0.5.0.
• Viewer managed file version reports 0.5.0.0; product/informational version begins with 0.5.0.

This PR only prepares the version. It does not create or push the release tag.

[asklar]

Holding the release version bump while MCP visual-tree notifications, Viewer migration from watch to MCP, and visual-tree property editing are completed in a preceding PR.