[TerminalSandboxing]: Include workspace folders as default in the sandbox config

[dileepyavan]

fixes #302904

This PR adds the multi root workspace folders as default to the sandbox config

[Copilot]

Pull request overview

This PR updates the terminal sandbox config generation so that workspace folder paths are included in the default filesystem allowWrite list, and ensures the config is refreshed when workspace folders change (multi-root support).

Changes:

• Add IWorkspaceContextService dependency to TerminalSandboxService and refresh sandbox config on workspace folder changes.
• Include current workspace folder paths in the generated sandbox filesystem allowWrite list.
• Extend unit tests with a workspace context service mock and a test covering config refresh on folder changes.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/vs/workbench/contrib/terminalContrib/chatAgentTools/common/terminalSandboxService.ts	Adds workspace-folder-driven allowWrite defaults and triggers config regeneration on workspace folder changes.
src/vs/workbench/contrib/terminalContrib/chatAgentTools/test/browser/terminalSandboxService.test.ts	Adds workspace context mocking and a test asserting config refresh behavior when workspace folders change.

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