Remove redundant @vscode/vsce uninstall/reinstall from postinstall

[Copilot]

The postinstall script had a workaround that uninstalled and reinstalled @vscode/vsce after every npm install to fix a missing out/ directory issue in older versions. This was resolved by the upgrade to @vscode/vsce@^3.7.1 in v1.0.71, making the workaround dead weight.

• Simplified postinstall to only install client dependencies:

-"postinstall": "cd client && npm install && cd .. && npm uninstall @vscode/vsce && npm install --save-dev @vscode/vsce"
+"postinstall": "cd client && npm install"

Original prompt

The package.json command for the vs code extension currently uses an npm install command for vsce that was to try to work around a strange issue where even after installing the dependencies bits of vsce were missing. This is however kind of messy and it would be better to remove this strangeness of having an uninstall and reinstll in the build script. Please investigte and try to fix the pack-ext build steps to remove the explicit install and uninstall steps that should alredy have been covered by the original npm install.

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