feat(app): start the Assistant minimized on desktop (0289) - #445

## What

`@xnetjs/devkit`'s `NodeCommandRunner` now scrubs git's repo-location
environment variables (`GIT_DIR`, `GIT_WORK_TREE`, `GIT_INDEX_FILE`, and
friends) for `git` invocations, so the explicit `cwd` is always
authoritative. An explicit `options.env` entry still wins.

## Why

`RunOptions.cwd` is required precisely so a caller "can never
accidentally run in `process.cwd()`" — but git reads
`GIT_DIR`/`GIT_WORK_TREE`/`GIT_INDEX_FILE` from the environment **over**
`cwd`. A husky hook (`pre-commit`/`pre-push`) exports exactly those vars
pointing at the hook's repo. So when the pre-push hook runs `pnpm test`,
devkit's real-repo tests (`git.test.ts`) spawned `git` children that
inherited the hook's `GIT_DIR` and operated on the **actual worktree**
instead of their temp repo — running `git config`, `git commit`, and
even `git push` against it.

This was not hypothetical: it clobbered a live worktree and its remote
branch during PR #445 (and recurred on #444) — the worktree's
`user.name`/`email` got overwritten and junk `initial`/`checkpoint`
commits were pushed to origin.

## How

- `command-runner.ts`: for `command === 'git'`, merge `{ ...process.env,
...<git-location vars set to undefined>, ...options.env }`. Node's
`spawn` omits `undefined`-valued env keys, so the inherited leak is
dropped while any explicit override is preserved. The scrubbed set is
documented in the new `GIT_LOCATION_ENV` (module-internal — not added to
the package barrel, so no public API change → **patch**).

## Tests

- `command-runner.test.ts`: with a leaked bogus `GIT_DIR`, `git
rev-parse --is-inside-work-tree` still resolves the `cwd` repo (would be
fatal without the scrub); and an explicit `options.env` `GIT_DIR` still
wins.
- `git.test.ts`: a `checkpoint()` lands in `cwd` while `GIT_*` points at
a decoy, and the decoy never becomes a repo.
- Ran the two devkit test files directly (13 passing). Did **not** run
the full suite locally, to avoid re-triggering the very leak this fixes
on an unpatched checkout.

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