Fix: hierarchy click should only open Class definition, not the source file

[MatiasFernandez]

Summary

Clicking a class in the System Browser's hierarchy view opened both the Class Definition panel and the on-disk .gs Topaz cache file for that class. This shoved a redundant read-only tab in front of whatever the user was actively editing. The column-view click already only opened the definition — the hierarchy click should behave the same way.

Changes

• Removed the extra openClassFile call from the hierarchy-click handler in client/src/systemBrowser.ts, so it now only calls applyClassSelection, matching column-click behavior.
• Updated surrounding comments to reflect that both the column click and hierarchy click are definition-only.
• Added a regression test in client/src/__tests__/systemBrowser.test.ts asserting that selecting a hierarchy class does not trigger showTextDocument.

Addresses Gitlab#36.

Test plan

• npm run compile && npm test passes
• Manually tested in the extension: clicking a class in the hierarchy view now only opens/refreshes the Class Definition panel and no longer opens a redundant source file tab, confirming the fix works as intended.