Shell tool injects NODE_ENV=production into every spawned command, breaking dev/test tooling #971

- Command Code on Windows (win32)
- Shell tool: PowerShell 5.1
- NODE_ENV not set at Machine or User scope

## Problem
Every command executed through the shell/powershell tool runs with
`NODE_ENV=production`, even though the user's own shell has it unset.
This causes commands to fail in the tool that succeed in the user's
terminal.

## Reproduction
Check the value in any shell tool call:

    $env:NODE_ENV
    # -> production

Then check where it comes from:

    [Environment]::GetEnvironmentVariable('NODE_ENV','Machine')  # -> empty
    [Environment]::GetEnvironmentVariable('NODE_ENV','User')     # -> empty
    [Environment]::GetEnvironmentVariable('NODE_ENV','Process')  # -> production

## Root cause
`NODE_ENV` is present at **Process** scope only. Machine and User scopesare both empty, so it is not inherited from the Windows environment

## Impact
Tooling reads `NODE_ENV` to decide dev vs. prod behavior. With it pinned
to `production`, commands that work in the user's terminal fail or behave
differently:

- **npm/pnpm/yarn skip `devDependencies`** on install, so build/test/lint
  binaries (vitest, eslint, tsx, typescript) are missing -> "command not found"
  or unresolved imports
- **Vite** switches to production optimization paths, dropping
  `NODE_ENV === 'development'` branches, dev-only warnings, and HMR wiring
- **react-refresh / ts-node / nodemon** change transpilation and reload behavior
- Test runs may execute production-only code paths

## ScopeThis affects only subprocesses spawned by the shell tool. The user's
interactive shell is unaffected (`NODE_ENV` is genuinely unset there).
The asymmetry is the confusing part: the same command works for the user
and fails for the agent, with no visible difference in the command itself.

The shell tool should not inject `NODE_ENV=production` into spawned
commands. Either:
- don't set it at all, letting the user/system environment pass through, or
- make it opt-in / configurable per session

## Additional context
Verified in a live session: `NODE_ENV=production` at process scope,
empty at machine and user scope.