Support non-interactive Python environment configuration

[eleanorjboyd]

Fixes #25940

Summary

• Adds an optional pythonPath input to configure_python_environment, allowing agents to select a known interpreter without opening blocking UI.
• Validates the interpreter before changing settings, waits for the correctly scoped active-environment event, handles an already-active interpreter without delay, and verifies the switch before reporting success.
• Propagates cancellation through environment selection, virtual-environment creation waits, and environment-resolution polling.
• Fixes the virtual-environment resolution loop so it stops after its timeout.
• Adds focused unit coverage for direct selection, invalid paths, cancellation, already-active environments, event ordering, and multi-root isolation.

Validation

• Prettier
• TypeScript type-check
• ESLint
• 12 focused unit tests

[Copilot]

Pull request overview

This PR enhances the Python environment configuration chat tools to optionally accept a pythonPath so the interpreter can be set directly (skipping interactive UI), which is particularly useful for autopilot/bypass-approvals flows.

Changes:

• Add optional pythonPath support to configure_python_environment and selectEnvironment tools (plus input schema updates in package.json).
• Wrap additional operations with raceCancellationError to better respect cancellation tokens.
• Fix virtual environment resolution polling loop condition and adjust venv creation options.

Show a summary per file

File	Description
src/client/chat/selectEnvTool.ts	Adds pythonPath fast-path and wraps UI selection flows with cancellation handling.
src/client/chat/createVirtualEnvTool.ts	Improves cancellation handling, tweaks venv creation options, and fixes the env-resolution polling loop condition.
src/client/chat/configurePythonEnvTool.ts	Adds pythonPath argument + direct interpreter setup path, updates tool argument typing.
package.json	Extends language model tool schemas/descriptions to document and accept pythonPath.

Copilot's findings

Comments suppressed due to low confidence (1)

src/client/chat/selectEnvTool.ts:87

• After calling updateActiveEnvironmentPath, the code immediately calls getActiveEnvironmentPath()/resolveEnvironment(). updateActiveEnvironmentPath only updates configuration; the active environment change is asynchronous (see code that waits on onDidChangeActiveEnvironmentPath, e.g. venvSwitchPython.ts). This fast-path can therefore resolve and return details for the previous environment. Wait for this.api.onDidChangeActiveEnvironmentPath (matching pythonPath) or otherwise confirm the switch before resolving/returning environment details.

            await raceCancellationError(
                this.api.updateActiveEnvironmentPath(options.input.pythonPath, resource),
                token,
            );
            const env = await raceCancellationError(
                this.api.resolveEnvironment(this.api.getActiveEnvironmentPath(resource)),
                token,
            );

• Files reviewed: 4/4 changed files
• Comments generated: 3