fix(rolldown): run the devtools build with a production NODE_ENV

[zahidzorbaz]

Description

The Rolldown panel's Run build with devtools produced a development bundle. The button spawns vite build from the running dev server, and the hub's startChildProcess() passes the parent env through, so the child inherits the NODE_ENV=development that Vite sets for the dev server. vite build keeps an already-set NODE_ENV and replaces process.env.NODE_ENV with process.env.NODE_ENV || mode, so every library's dev-only branches stayed in the bundle the panel then analysed.

getBuildCommand() now sets NODE_ENV: 'production', which is what a plain vite build resolves to. The confirmation dialog shows it too: NODE_ENV=production VITE_DEVTOOLS_ROLLDOWN=true vite build.

The hub keeps passing the env through, since terminal sessions generally need the parent env (PATH, proxies, user variables). The build runner is the caller that knows the build must not inherit the dev server's NODE_ENV.

Linked Issues

Fixes #586

Additional context

• Tests: packages/rolldown/src/node/rolldown/__tests__/build-runner.test.ts checks getBuildCommand() and the options startBuild() passes to startChildProcess(). Both fail on main.
• Vite 8.3.0 behaviour checked with a two-line app: vite build drops an if (process.env.NODE_ENV !== 'production') branch, while NODE_ENV=development vite build keeps it.
• Impact seen in a real Vue app: first-load JS 259.2 KB gz via the button vs 200.9 KB gz for a plain vite build of the same commit (@vue/devtools-kit only in the former).
• Gates on Windows 11 / Node 24.21: pnpm lint, pnpm typecheck and pnpm build pass. pnpm test passes except the two locale-dependent packages/ui bytesToHumanSize cases, which fail the same way on a clean main here (tr-TR locale).

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