[BUG] Extra file JSON object passed via CLI --extra-files parameter is improperly parsed

#### Environment details

- OS: macOS 15.3 (Darwin 24.3.0)
- Node.js version: v22.13.0
- npm version: v10.9.2
- `release-please` version: 17.0.0

**Issue:**

When passing an object via the `--extra-files` parameter (for example, an object with `"type": "yaml"`, `"path": "scripts/helm/dev-ext/sa-east-1/values.yaml"`, `"jsonpath": "$.rollout-Canary.image.tag"` and `"glob": false`), Release Please appears to parse each property separately as a file path. Instead of treating the JSON object as a single extra file configuration, its keys and values are fetched individually from the target branch.

**Reproduction:**
1. Run the following command (using zsh):
```
release-please release-pr \
--repo-url="https://github.com/myOrg/myRepo" \
--token "****************************************" \
--release-type=simple \
--pull-request-header="My custom pull request header" \
--extra-files='[{"type":"yaml","path":"scripts/helm/dev-ext/sa-east-1/values.yaml","jsonpath":"$.rollout-Canary.image.tag","glob":false}]'
```
2. Observe in the logs that Release Please tries to fetch:
- `{type:"yaml"`
- `path:"scripts/helm/dev-ext/sa-east-1/values.yaml"`
- `jsonpath:"$.rollout-Canary.image.tag"`
- `glob:false}`
as separate files from branch `main`.

```
❯ type: simple
❯ targetBranch: main
❯ commits: 2
✔ Considering: 2 commits
❯ component:
❯ pull request title pattern: undefined
❯ componentNoSpace: false
✔ Looking for open release pull requests
✔ found 0 open release pull requests.
✔ Looking for snoozed release pull requests
✔ found 0 snoozed release pull requests.
❯ Fetching CHANGELOG.md from branch main
❯ Fetching version.txt from branch main
⚠ file version.txt did not exist
❯ Fetching {type:"yaml" from branch main
⚠ file {type:"yaml" did not exist
❯ Fetching path:"scripts/helm/dev-ext/sa-east-1/values.yaml" from branch main
⚠ file path:"scripts/helm/dev-ext/sa-east-1/values.yaml" did not exist
❯ Fetching jsonpath:"$.rollout-Canary.image.tag" from branch main
⚠ file jsonpath:"$.rollout-Canary.image.tag" did not exist
❯ Fetching glob:false} from branch main
⚠ file glob:false} did not exist
❯ Fetching .release-please-manifest.json from branch main
⚠ file .release-please-manifest.json did not exist
✔ Starting GitHub PR workflow...
```

**Expected Behavior:**

The JSON array containing the extra file object should be parsed correctly. The CLI should use the `"type"` field to determine the updater (e.g., `GenericYaml` for `"yaml"` type) and apply the `"jsonpath"` to update the file content, rather than treating the object properties as independent file paths.

The CLI should pick up the `--extra-files` parameter as a valid JSON array containing a single object. That object should then be processed by the `extraFilePaths` and `extraFileUpdates` methods (see attached snippet from base.ts), determining the file paths and updater type without fetching individual object properties from the branch.

**Context:**

Looking at the source code in base.ts, the method `extraFilePaths(extraFile: ExtraFile)` expects an object but then processes it in a way that suggests the entire object should represent a single extra file. The behavior above indicates that the passed JSON isn’t being recognized as an object with keys but rather as separate string inputs.

### Requirements

I'm using the CLI with the `--extra-files` parameter instead of a configuration file or manifest because in our CI pipeline we don't expect to have both files in the repository. We need this behavior to override options locally. I have also tested using a configuration file, but every time the CLI still attempts to fetch the file remotely from the main branch. I'm open to learning if there's a way to override some config or manifest options using local files, but currently, my goal is to pass the extra file data directly via the CLI.

### Additional Context

Below is a brief excerpt from `base.ts` where the extra files are processed:

```typescript
// Helper to convert extra files with globs to the file paths to add
private async extraFilePaths(extraFile: ExtraFile): Promise {
if (typeof extraFile !== 'object') {
return [extraFile];
}
if (!extraFile.glob) {
return [extraFile.path];
}
if (extraFile.path.startsWith('/')) {
return (
await this.github.findFilesByGlobAndRef(
extraFile.path.slice(1),
this.targetBranch
)
).map(file => `/${file}`);
} else if (this.path === ROOT_PROJECT_PATH) {
return this.github.findFilesByGlobAndRef(
extraFile.path,
this.targetBranch
);
} else {
return this.github.findFilesByGlobAndRef(
extraFile.path,
this.targetBranch,
this.path
);
}
}
```

Also this following code when the GenericYaml CompositeUpdate is called:
```typescript
protected async extraFileUpdates(
version: Version,
versionsMap: VersionsMap,
dateFormat: string
): Promise {
const extraFileUpdates: Update[] = [];
for (const extraFile of this.extraFiles) {
if (typeof extraFile === 'object') {
const paths = await this.extraFilePaths(extraFile);
for (const path of paths) {
switch (extraFile.type) {
case 'generic':
extraFileUpdates.push({
path: this.addPath(path),
createIfMissing: false,
updater: new Generic({
version,
versionsMap,
dateFormat: dateFormat,
}),
});
break;
case 'json':
extraFileUpdates.push({
path: this.addPath(path),
createIfMissing: false,
updater: new GenericJson(extraFile.jsonpath, version),
});
break;
case 'yaml':
extraFileUpdates.push({
path: this.addPath(path),
createIfMissing: false,
updater: new GenericYaml(extraFile.jsonpath, version),
});
break;

[...]

default:
throw new Error(
`unsupported extraFile type: ${
(extraFile as {type: string}).type
}`
);
}
}
} else if (extraFile.endsWith('.json')) {
extraFileUpdates.push({
path: this.addPath(extraFile),
createIfMissing: false,
updater: new CompositeUpdater(
new GenericJson('$.version', version),
new Generic({version, versionsMap, dateFormat: dateFormat})
),
});
} else if (extraFile.endsWith('.yaml') || extraFile.endsWith('.yml')) {
extraFileUpdates.push({
path: this.addPath(extraFile),
createIfMissing: false,
updater: new CompositeUpdater(
new GenericYaml('$.version', version),
new Generic({version, versionsMap, dateFormat: dateFormat})
),
});

[...]

} else {
extraFileUpdates.push({
path: this.addPath(extraFile),
createIfMissing: false,
updater: new Generic({version, versionsMap, dateFormat: dateFormat}),
});
}
}
return extraFileUpdates;
}
```

This issue suggests that the CLI does not recognize the JSON object as a whole, and each property ends up being treated as a separate file.

Any help or guidance to resolve this behavior would be appreciated.