Add language server restart command and bundle packaging

[robknopf]

Summary

Add a command to restart the Zen C language server from VS Code, and clean up extension packaging to use the bundled entrypoint.

Changes

• add Zen C: Restart Language Server command to the Command Palette
• refactor the extension client lifecycle so the language client can be stopped and restarted
• switch packaging to use the bundled out/main.js entrypoint
• run bundling during vscode:prepublish
• change compile to typecheck-only with tsc --noEmit
• tighten .vscodeignore so the VSIX excludes node_modules and repo-only artifacts
• update local @vscode/vsce to the current release used for packaging

Verification

• npm run compile
• npm run bundle
• npm run package
• verified the VSIX contents were reduced to the bundled runtime assets