(spec2cdk): Alpha module directory naming convention prevents grants.json processing for aws-bedrock-agentcore-alpha

### Describe the feature

When an alpha module's directory name doesn't match the CloudFormation namespace naming convention, `spec2cdk` cannot locate the `grants.json` file, preventing the generation of `*-grants.generated.ts` files.

**Current behavior in spec2cdk:**
```typescript
// tools/@aws-cdk/spec2cdk/lib/generate.ts
function grantsConfigForModule(moduleName, modulePath, isStable) {
const grantsFileLocation = isStable
? path.join(modulePath, moduleName)
: path.join(modulePath, '..', `${moduleName}-alpha`);
// ...
}
```

For `AWS::BedrockAgentCore`:
- `moduleName` derived from CF namespace: `aws-bedrockagentcore`
- Expected directory: `aws-bedrockagentcore-alpha`
- Actual directory: `aws-bedrock-agentcore-alpha`

This mismatch causes `grants.json` to not be found.

### Use Case

I want to implement the recommended grant pattern using `grants.json` for `@aws-cdk/aws-bedrock-agentcore-alpha` module to generate type-safe grant methods (e.g., `grantInvokeRuntime()`).

Currently, `aws-elasticache-alpha` works correctly because:
- CF namespace: `AWS::ElastiCache` → `aws-elasticache`
- Directory: `aws-elasticache-alpha` ✓ (matches)

But `aws-bedrock-agentcore-alpha` fails because:
- CF namespace: `AWS::BedrockAgentCore` → `aws-bedrockagentcore`
- Directory: `aws-bedrock-agentcore-alpha` ✗ (hyphen mismatch)

### Proposed Solution

**Option 1:** Rename the directory to `aws-bedrockagentcore-alpha`
- Pros: Follows the convention
- Cons: Breaking change for existing users

**Option 2:** Add a mapping/alias mechanism in spec2cdk
- Allow `grants.json` lookup to handle directory name variations
- Could use package.json metadata or a separate mapping file

### Acknowledgements

- [x] I may be able to implement this feature request
- [x] This feature might incur a breaking change

### AWS CDK Library version (aws-cdk-lib)

`2.238.0`

### AWS CDK CLI version

N/A

### Environment details

N/A

Start in tools/@aws-cdk/spec2cdk/lib/generate.ts, especially grantsConfigForModule, and trace how the module path and grants.json location are derived. Compare the aws-bedrockagentcore namespace with the aws-bedrock-agentcore-alpha directory, then determine whether a directory rename or mapping mechanism fits the existing package layout. Done means spec2cdk locates grants.json and generates the module's *-grants.generated.ts file.

Written by the indexing model from the issue text.