chore: prepare v2.5.2 release

[CoderLambert]

Summary

Version surfaces aligned to 2.5.2 for the Omarchy plugin-directory compatibility fix (merged via #14 and #15).

Changes

• manifest.json → 2.5.2
• bin/qopen VERSION → 2.5.2
• README.md / README.zh-CN.md current release → 2.5.2
• CHANGELOG.md — new [2.5.2] section; [Unreleased] left empty

What ships in this release

Recent Omarchy versions sanitize third-party plugin manifests and remove the
internal __sourceDir field, so older QOpen releases opened with
0 resources. QOpen now:

• falls back to the scoped pluginRegistry.entryPointUrl(...) API;
• derives the plugin root from the complete menu entry-point path (correct
  even if the entry point later moves to a subdirectory such as ui/QOpen.qml);
• only derives backend paths from local file:// URLs;
• keeps the old __sourceDir path for backward compatibility.

The personal catalog requires no migration — ~/.config/qopen/config.json
is untouched by plugin updates.

Automated validation

• python -m json.tool manifest.json OK
• python -m py_compile bin/qopen OK
• python -m unittest discover -s tests -v — 49 tests OK
• omarchy plugin validate . — exit 0
• qmlcachegen --only-bytecode on all five QML files OK
• git diff --check clean
• ./bin/qopen --version → qopen 2.5.2

Runtime acceptance for the fix itself was performed on a live omarchy 4.0.4
shell by the maintainer before this release.

🤖 Generated with Claude Code