chat: avoid redundant environment tool confirmation

[Yashraj Jangra (Yashraj-Jangra)]

Summary

• Remove the extra confirmation modal displayed before launching the Python environment picker in SelectPythonEnvTool.
• Allow tool invocation preparation to return an empty object directly, preserving explicit environment creation/selection choices inside the quick pick dialog.
• Add regression unit test coverage in src/test/chat/selectEnvTool.unit.test.ts.

Rationale

The configurePythonEnvironment tool currently prompts the user with an extra confirmation dialog during tool preparation. Since the environment picker itself requires explicit user selection and approval before modifying any environment, the preceding confirmation step is redundant and unnecessarily blocks automated/allow-all tool flows.

Testing

• Added selectEnvTool.unit.test.ts to test that prepareInvocation does not return confirmationMessages.
• Ran unit tests: npx mocha --config ./build/.mocha.unittests.json --grep "Select Python Environment Tool" (1 passing).
• Checked code formatting and linting: npm run lint (passed cleanly).