fix(api): Isolate API package validation consumers from ambient type definitions

[Satyam Pandey (SatyamPandey-07)]

Related Issue

Fixes #1799

Changes Proposed

• [API Test Configurations]: Configured "types": ["node", "vscode"] and "typeRoots": ["../node_modules/@types"] in api/test/tsconfig.modern.json and api/test/tsconfig.legacy.json to prevent tsc from traversing parent directories for ambient type definitions.
• [Test Package Runner]: Updated api/scripts/test-package.cjs to resolve typescript/bin/tsc dynamically via createRequire instead of hardcoding packageRoot/node_modules/typescript/bin/tsc.
• [API Package Scripts]: Added "test": "npm run test:package" to api/package.json so standard npm test runs package validation.

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

• Test A: npm --prefix api run test:package completed with 0 errors (modern and legacy consumers verified).
• Test B: npm --prefix api test ran successfully.
• Test C: Root unit tests (npm run unittest) passed with 2,411 passing tests.
• Test D: Root linter (npm run lint) passed with 0 errors/warnings.
• Test E: TypeScript compilation (npm run compile-tests) succeeded with 0 errors.

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings

[Satyam Pandey (SatyamPandey-07)]

@microsoft-github-policy-service agree

[Satyam Pandey (SatyamPandey-07)]

Bill Schnurr (@bschnurr) Hi, just bumping this PR in case it slipped through your notifications. Let me know if you need any changes or further testing!