Fix/model config

[harshpreet931]

This pull request updates all import statements in test files to use explicit .js extensions for local module imports. This change ensures compatibility with ES module resolution, especially in environments that require explicit file extensions. The updates affect various test files across the codebase, including those for agents, tools, types, models, sessions, streaming, and validation.

Module import path updates:

• All test files in src/__tests__, src/a2a/__tests__, and src/adk/__tests__ now import local modules with the .js extension, e.g., from '../index.js' instead of from '../index'. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19]

Grouped by theme:

• Core test files: Updated imports in main test files for engine, agent, and HITL functionality. [1] [2] [3]
• A2A tests: Updated imports in agent, client, executor, integration, protocol, server, and types test files. [1] [2] [3] [4] [5] [6] [7]
• ADK tests: Updated imports in agents, content, integration, models, runners, schemas, sessions, and streaming test files. [1] [2] [3] [4] [5] [6] [7] [8]
• Validation policies: Updated import in validation test file to use .js extension.

This update helps avoid import errors and improves compatibility with modern JavaScript tooling and module systems.