1d45e62f30
On Windows npm prints only a terse summary on failure; the actual cause (postinstall stderr like Electron's install.js, network traces, EBUSY retries) lives in npm-cache\_logs\<ts>-debug-0.log, which never reached the Tauri bootstrap log. Field report: a fresh-VM desktop install died with 'npm error command node install.js' and zero actionable detail. Adds Write-NpmDebugLogTail: locates the debug log from npm's 'A complete log of this run' line (fallback: newest _logs/*-debug-*.log under 'npm config get cache') and replays its last 200 lines through our output stream, which the bootstrap installer's streaming sink captures. Wired at all four npm failure sites: desktop workspace npm ci/install, _Run-NpmInstall (browser tools), Install-AgentBrowser (--silent global install), and the desktop 'npm run pack' build step.