perf: `oxlint` and `oxfmt` each load `vite.config.ts` twice per invocation

### Describe the bug

A single `vp staged` run evaluates the project's `vite.config.ts` 8 times.

The repro puts a side effect at the top of the config that appends one line per evaluation, recording timestamp, pid and argv:

```ts
import { appendFileSync } from 'node:fs';

appendFileSync(
new URL('./config-loads.log', import.meta.url),
`load ${Date.now()} pid=${process.pid} argv=${process.argv.slice(1).join(' ')}\n`,
);

export default {
staged: { '*.ts': 'vp check --fix' },
};
```

With 3 staged `.ts` files, one `vp staged` run produces 8 lines (paths and arguments elided for width):

```log
load ... pid=137436 argv=.bin/vp staged
load ... pid=137479 argv=.bin/vp check --fix f1.ts f2.ts f3.ts
load ... pid=137513 argv=oxfmt/bin/oxfmt --no-error-on-unmatched-pattern f1.ts f2.ts f3.ts
load ... pid=137513 argv=oxfmt/bin/oxfmt --no-error-on-unmatched-pattern f1.ts f2.ts f3.ts
load ... pid=137573 argv=oxlint/bin/oxlint --fix --format=default --no-error-on-unmatched-pattern f1.ts f2.ts f3.ts
load ... pid=137573 argv=oxlint/bin/oxlint --fix --format=default --no-error-on-unmatched-pattern f1.ts f2.ts f3.ts
load ... pid=137654 argv=oxfmt/bin/oxfmt --no-error-on-unmatched-pattern f1.ts f2.ts f3.ts
load ... pid=137654 argv=oxfmt/bin/oxfmt --no-error-on-unmatched-pattern f1.ts f2.ts f3.ts
```

Four processes load the config, and `oxfmt` and `oxlint` each load it twice within the same pid.

Timings from the same repo and the same 3 staged files, averaged over 3 runs (`vp` v0.3.1, Node v26.8.2, bun 1.4.2):

| | Time |
| --- | --- |
| `oxfmt` then `oxlint`, invoked directly | 0.045s |
| `vp check --fix`, no `vite.config.ts` present | 0.156s |
| `vp check --fix`, one-line static `vite.config.ts` | 0.957s |
| `vp check --fix`, instrumented `vite.config.ts` | 0.917s |
| `vp staged`, no-op task | 0.274s |
| `vp staged`, running `vp check --fix` | 1.004s |

The config used for the 0.957s row has no imports, no plugins and no side effects:

```ts
export default { staged: { '*.ts': 'vp check --fix' } };
```

So the difference between the 0.156s and 0.957s rows is attributable to the presence of the config file rather than to plugin evaluation, and `lazyPlugins` does not apply since there is nothing to lazy-load. The instrumented config measures the same as the one-line one, so the `appendFileSync` is not contributing meaningfully.

Adding `.oxlintrc.json` and `.oxfmtrc.json` reduces `vp check --fix` to 0.680s but does not eliminate the loads: the config is still evaluated 7 times in a single run.

`vite.config.ts` is expected to evaluate once per `vp staged` run, or the result is cached and reused across the processes that need it.

### Reproduction

https://github.com/ryansuhartanto/vite-plus-staged-perf

### Steps to reproduce

After cloning:

```sh
bun install
./bench.sh
```

### System Info

```shell
VITE+ - The Unified Toolchain for the Web

vp v0.3.0

Local vite-plus:
vite-plus v0.3.1

Tools:
vite v8.2.2
rolldown v1.2.7
vitest v4.1.11
oxfmt v0.66.0
oxlint v1.81.0
oxlint-tsgolint v7.0.2001
tsdown v0.23.0
```

### Used Package Manager

bun

### Logs

```shell

```

### Validations

- [x] Read the [Contributing Guidelines](https://github.com/voidzero-dev/vite-plus/blob/main/CONTRIBUTING.md).
- [x] Check that there isn't [already an issue](https://github.com/voidzero-dev/vite-plus/issues) for the same bug.
- [x] Confirm this is a Vite+ issue and not an upstream issue (Vite, Vitest, tsdown, Rolldown, or Oxc).
- [x] The provided reproduction is a [minimal reproducible example](https://stackoverflow.com/help/minimal-reproducible-example).

Inizia con la riproduzione collegata ed esegui bench.sh per osservare la valutazione ripetuta di vite.config.ts. Traccia le invocazioni di vp staged e vp check --fix, quindi verifica che una singola esecuzione valuti la configurazione una volta oppure riutilizzi un risultato memorizzato nella cache tra i processi che ne hanno bisogno.

Scritto dal modello di indicizzazione a partire dal testo della issue.