Allow `vp staged` to resolve workspace-root config from subdirectories

### Description

In a monorepo, `vp staged` fails when invoked from a workspace package if the `staged` config exists only in the workspace-root `vite.config.ts`.

This is common with coding agents: after inspecting or editing one package, they often keep that package as the working directory when running validation commands.

```text
repo/
├── package.json # workspaces: ["packages/*"]
├── vite.config.ts # contains staged config
└── packages/
└── app/
└── src/index.ts
```

```ts
// repo/vite.config.ts
export default {
staged: {
'*.{js,ts,tsx}': 'vp check --fix',
},
}
```

```sh
git add packages/app/src/index.ts
cd packages/app
vp staged
```

Actual result:

```text
error: No "staged" config found in vite.config.ts. Please add a staged config
```

A normal pre-commit hook usually hides this behavior because Git starts client-side hooks from the worktree root, regardless of where `git commit` was entered.

### Current behavior

The following was verified with an isolated Git monorepo:

| Invocation | Config | File/task scope |
| --- | --- | --- |
| Run from repository root | Root `vite.config.ts` | Repository |
| Run from a package with no local `staged` config | None; exits with an error | Nothing runs |
| Run from a package with a local `staged` config | Package config | Package CWD |
| Run from a package with `--cwd ` | Root config | Repository |
| Run through a Git pre-commit hook | Root config, because Git uses the worktree root | Repository |

Internally, Vite+ resolves one `staged` object from the invocation CWD and passes it through lint-staged's programmatic `config` option. lint-staged still resolves the Git repository and staged files, but its own multi-config discovery is bypassed.

### Ecosystem patterns

Existing tools use different models:

| Model | Tools | Behavior |
| --- | --- | --- |
| Hook manager | Git, Husky, simple-git-hooks | Git starts hooks at the worktree root. The manager executes a literal hook command; package-specific CWD or filtering is left to that command. |
| Central root config | pre-commit, Lefthook | The tool resolves the Git root and loads a repository-level config. Package behavior is expressed through filters or per-command root settings. |
| Distributed config | lint-staged | The tool can discover multiple configs, assign each staged file to its closest config, and run tasks from the selected config directory. Configs are isolated rather than merged. |
| Current Vite+ behavior | `vp staged` | Git state is repository-aware through lint-staged, while Vite config lookup remains limited to the invocation CWD. |

Relevant details:

- Git changes to the worktree root before client-side hooks: https://git-scm.com/docs/githooks
- Husky requires an explicit `cd` when a hook should run inside a nested project: https://typicode.github.io/husky/how-to.html#project-not-in-git-root-directory
- lint-staged documents closest-config selection, isolated configs, config-directory task CWD, and package scoping with `--cwd`: https://github.com/lint-staged/lint-staged#how-to-use-lint-staged-in-a-multi-package-monorepo
- Lefthook loads from the Git root and uses a command-level `root` option to change CWD and filter files; globs remain relative to the Git root: https://lefthook.dev/configuration/root/
- pre-commit resolves the Git top level and changes into it before running most commands: https://github.com/pre-commit/pre-commit/blob/main/pre_commit/main.py#L175-L199

### Design choices

There are two separate decisions. This issue does not propose a preferred combination.

#### 1. Where should config come from?

- **Current CWD only:** preserve existing behavior; improve documentation/error output and require callers to use root CWD or `--cwd`.
- **Workspace/Git root:** always use one central root policy.
- **Nearest ancestor config:** walk upward to the workspace root. This could stop at the first Vite config, or continue until finding one that defines `staged`.
- **Multiple configs:** discover package/root staged configs and assign files to them independently.
- **Explicit selection:** add an option such as `--config` or `--root`; this can supplement any implicit rule.

Important edge case: a package may have a `vite.config.ts` for build settings but keep `staged` only at the workspace root. “Nearest Vite config” and “nearest config defining staged” produce different results.

#### 2. What should the execution scope be?

- **Repository root:** task CWD, glob base, and staged-file scope all use the root.
- **Invocation directory:** an inherited/root config can be used while files and tasks remain scoped to the package from which the command was launched.
- **Config directory:** tasks and file matching follow whichever config was selected.

These choices have different consequences. Root scope may process staged files in sibling packages; invocation scope may run root-defined commands from a package CWD; config-directory scope becomes more complex if multiple configs are supported.

Possible combinations include:

- root config + root scope;
- nearest ancestor config + invocation scope;
- current behavior + an explicit config/root option;
- multiple configs + per-config task scope.

### Relevant implementation

- Current staged config resolution and inline lint-staged config: https://github.com/voidzero-dev/vite-plus/blob/main/packages/cli/src/staged/bin.ts#L139-L164
- Existing workspace-bounded config traversal: https://github.com/voidzero-dev/vite-plus/blob/main/packages/cli/src/resolve-vite-config.ts#L98-L115
- Existing use of traversal in `vp pack`: https://github.com/voidzero-dev/vite-plus/blob/main/packages/cli/src/pack-bin.ts#L148-L150

### Validations

- [x] Read the [Contributing Guidelines](https://github.com/voidzero-dev/vite-plus/blob/main/CONTRIBUTING.md).
- [x] Confirm this request is for Vite+ itself and not for Vite, Vitest, tsdown, Rolldown, or Oxc.
- [x] Checked that there is not already an open issue requesting the same behavior.

Bắt đầu với packages/cli/src/staged/bin.ts, sau đó đọc cơ chế duyệt giới hạn trong workspace ở packages/cli/src/resolve-vite-config.ts và cách nó được sử dụng trong packages/cli/src/pack-bin.ts. Tái hiện kịch bản root-config-from-package được mô tả ở trên, rồi thiết lập và xác thực một chính sách duy nhất về việc phân giải config và phạm vi thực thi, bao gồm cả trường hợp biên của Vite config cục bộ trong package.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.